text: # Copyright 2016 - Parsely, Inc. (d/b/a Parse.ly)
  #
  # Licensed 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.
  '''generator.py: API for defining generic sources in python'''
  from abc import abstractmethod
  
  class Generator:
    """API for defining a generic source for Heron in the Python Streamlet API
    """
  
    @abstractmethod
    def setup(self, context):
      """Called when a task for this operator is initialized within a worker on the cluster
  
      It provides the operator with the environment in which the operator executes.
      This should be used to initialize any custom variables or connection to databases.
  
      :type context: :class:`Context`
      :param context: This object can be used to get information about this task's place within the
                      topology, including the task id and component id of this task, input and output
                      information, etc.
      **Must be implemented by a subclass, otherwise NotImplementedError is raised.**
      """
      raise NotImplementedError("Generator not implementing setup() method.")
  
    @abstractmethod
    def get(self):
      """Generate the next element
      If there is nothing at the moment to generate, return None
  
      **Must be implemented by a subclass, otherwise NotImplementedError is raised.**
  
      """
      raise NotImplementedError("Generator not implementing get() method.")
  