Added naturally_equivalent to main module import

sqlalchemy_utils/__init__.py

@@ -6,6 +6,7 @@ from .functions import (
     escape_like,
     identity,
     primary_keys,
+    naturally_equivalent,
     render_statement,
     render_expression,
     create_mock_engine,
@@ -59,6 +60,7 @@ __all__ = (
     identity,
     instrumented_list,
     merge,
+    naturally_equivalent,
     primary_keys,
     proxy_dict,
     render_statement,