230 lines
9.3 KiB
Python
230 lines
9.3 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import logging
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from .enabled import EnabledExtensionManager
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from .exception import NoMatches
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LOG = logging.getLogger(__name__)
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class DispatchExtensionManager(EnabledExtensionManager):
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"""Loads all plugins and filters on execution.
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This is useful for long-running processes that need to pass
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different inputs to different extensions.
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:param namespace: The namespace for the entry points.
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:type namespace: str
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:param check_func: Function to determine which extensions to load.
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:type check_func: callable
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:param invoke_on_load: Boolean controlling whether to invoke the
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object returned by the entry point after the driver is loaded.
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:type invoke_on_load: bool
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:param invoke_args: Positional arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_args: tuple
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:param invoke_kwds: Named arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_kwds: dict
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:param propagate_map_exceptions: Boolean controlling whether exceptions
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are propagated up through the map call or whether they are logged and
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then ignored
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:type invoke_on_load: bool
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"""
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def map(self, filter_func, func, *args, **kwds):
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"""Iterate over the extensions invoking func() for any where
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filter_func() returns True.
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The signature of filter_func() should be::
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def filter_func(ext, *args, **kwds):
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pass
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The first argument to filter_func(), 'ext', is the
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:class:`~stevedore.extension.Extension`
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instance. filter_func() should return True if the extension
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should be invoked for the input arguments.
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The signature for func() should be::
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def func(ext, *args, **kwds):
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pass
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The first argument to func(), 'ext', is the
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:class:`~stevedore.extension.Extension` instance.
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Exceptions raised from within func() are propagated up and
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processing stopped if self.propagate_map_exceptions is True,
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otherwise they are logged and ignored.
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:param filter_func: Callable to test each extension.
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:param func: Callable to invoke for each extension.
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:param args: Variable arguments to pass to func()
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:param kwds: Keyword arguments to pass to func()
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:returns: List of values returned from func()
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"""
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if not self.extensions:
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# FIXME: Use a more specific exception class here.
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raise NoMatches('No %s extensions found' % self.namespace)
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response = []
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for e in self.extensions:
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if filter_func(e, *args, **kwds):
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self._invoke_one_plugin(response.append, func, e, args, kwds)
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return response
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def map_method(self, filter_func, method_name, *args, **kwds):
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"""Iterate over the extensions invoking each one's object method called
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`method_name` for any where filter_func() returns True.
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This is equivalent of using :meth:`map` with func set to
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`lambda x: x.obj.method_name()`
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while being more convenient.
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Exceptions raised from within the called method are propagated up
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and processing stopped if self.propagate_map_exceptions is True,
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otherwise they are logged and ignored.
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.. versionadded:: 0.12
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:param filter_func: Callable to test each extension.
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:param method_name: The extension method name to call
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for each extension.
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:param args: Variable arguments to pass to method
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:param kwds: Keyword arguments to pass to method
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:returns: List of values returned from methods
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"""
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return self.map(filter_func, self._call_extension_method,
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method_name, *args, **kwds)
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class NameDispatchExtensionManager(DispatchExtensionManager):
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"""Loads all plugins and filters on execution.
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This is useful for long-running processes that need to pass
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different inputs to different extensions and can predict the name
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of the extensions before calling them.
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The check_func argument should return a boolean, with ``True``
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indicating that the extension should be loaded and made available
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and ``False`` indicating that the extension should be ignored.
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:param namespace: The namespace for the entry points.
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:type namespace: str
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:param check_func: Function to determine which extensions to load.
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:type check_func: callable
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:param invoke_on_load: Boolean controlling whether to invoke the
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object returned by the entry point after the driver is loaded.
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:type invoke_on_load: bool
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:param invoke_args: Positional arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_args: tuple
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:param invoke_kwds: Named arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_kwds: dict
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:param propagate_map_exceptions: Boolean controlling whether exceptions
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are propagated up through the map call or whether they are logged and
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then ignored
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:type invoke_on_load: bool
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:param on_load_failure_callback: Callback function that will be called when
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an entrypoint can not be loaded. The arguments that will be provided
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when this is called (when an entrypoint fails to load) are
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(manager, entrypoint, exception)
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:type on_load_failure_callback: function
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:param verify_requirements: Use setuptools to enforce the
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dependencies of the plugin(s) being loaded. Defaults to False.
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:type verify_requirements: bool
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"""
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def __init__(self, namespace, check_func, invoke_on_load=False,
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invoke_args=(), invoke_kwds={},
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propagate_map_exceptions=False,
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on_load_failure_callback=None,
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verify_requirements=False):
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super(NameDispatchExtensionManager, self).__init__(
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namespace=namespace,
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check_func=check_func,
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invoke_on_load=invoke_on_load,
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invoke_args=invoke_args,
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invoke_kwds=invoke_kwds,
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propagate_map_exceptions=propagate_map_exceptions,
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on_load_failure_callback=on_load_failure_callback,
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verify_requirements=verify_requirements,
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)
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def _init_plugins(self, extensions):
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super(NameDispatchExtensionManager, self)._init_plugins(extensions)
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self.by_name = dict((e.name, e) for e in self.extensions)
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def map(self, names, func, *args, **kwds):
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"""Iterate over the extensions invoking func() for any where
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the name is in the given list of names.
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The signature for func() should be::
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def func(ext, *args, **kwds):
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pass
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The first argument to func(), 'ext', is the
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:class:`~stevedore.extension.Extension` instance.
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Exceptions raised from within func() are propagated up and
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processing stopped if self.propagate_map_exceptions is True,
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otherwise they are logged and ignored.
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:param names: List or set of name(s) of extension(s) to invoke.
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:param func: Callable to invoke for each extension.
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:param args: Variable arguments to pass to func()
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:param kwds: Keyword arguments to pass to func()
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:returns: List of values returned from func()
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"""
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response = []
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for name in names:
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try:
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e = self.by_name[name]
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except KeyError:
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LOG.debug('Missing extension %r being ignored', name)
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else:
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self._invoke_one_plugin(response.append, func, e, args, kwds)
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return response
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def map_method(self, names, method_name, *args, **kwds):
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"""Iterate over the extensions invoking each one's object method called
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`method_name` for any where the name is in the given list of names.
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This is equivalent of using :meth:`map` with func set to
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`lambda x: x.obj.method_name()`
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while being more convenient.
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Exceptions raised from within the called method are propagated up
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and processing stopped if self.propagate_map_exceptions is True,
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otherwise they are logged and ignored.
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.. versionadded:: 0.12
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:param names: List or set of name(s) of extension(s) to invoke.
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:param method_name: The extension method name
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to call for each extension.
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:param args: Variable arguments to pass to method
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:param kwds: Keyword arguments to pass to method
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:returns: List of values returned from methods
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"""
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return self.map(names, self._call_extension_method,
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method_name, *args, **kwds)
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