Add __hash__ method to Struct

kafka/protocol/struct.py

@@ -44,6 +44,9 @@ class Struct(AbstractType):
             key_vals.append('%s=%s' % (name, field.repr(self.__dict__[name])))
         return self.__class__.__name__ + '(' + ', '.join(key_vals) + ')'
 
+    def __hash__(self):
+        return hash(self.encode())
+
     def __eq__(self, other):
         if self.SCHEMA != other.SCHEMA:
             return False