text: #
  # Licensed to the Apache Software Foundation (ASF) under one or more
  # contributor license agreements.  See the NOTICE file distributed with
  # this work for additional information regarding copyright ownership.
  # The ASF licenses this file to You under the Apache License, Version 2.0
  # (the "License"); you may not use this file except in compliance with
  # the License.  You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  
  """A BeamPlugin base class.
  
  For experimental usage only; no backwards-compatibility guarantees.
  """
  
  
  class BeamPlugin(object):
    """Plugin base class to be extended by dependent users such as FileSystem.
    Any instantiated subclass will be imported at worker startup time."""
  
    @classmethod
    def get_all_subclasses(cls):
      """Get all the subclasses of the BeamPlugin class."""
      all_subclasses = []
      for subclass in cls.__subclasses__():
        all_subclasses.append(subclass)
        all_subclasses.extend(subclass.get_all_subclasses())
      return all_subclasses
  
    @classmethod
    def get_all_plugin_paths(cls):
      """Get full import paths of the BeamPlugin subclass."""
      def fullname(o):
        return o.__module__ + "." + o.__name__
      return [fullname(o) for o in cls.get_all_subclasses()]
  