new_contents: # -*- coding: utf-8 -*-
  
  # Copyright (c) 2015 Ericsson AB
  #
  # 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.
  
  from calvin.actor.actor import Actor, ActionResult, condition, guard
  
  
  class Alternate3(Actor):
      """
      Alternating between three streams of tokens
      Inputs:
        token_1 : first token stream
        token_2 : second token stream
        token_3 : third token stream
      Outputs:
          token : resulting token stream
      """
  
      def init(self):
          self.next_port = 1
  
      @condition(['token_1'], ['token'])
      @guard(lambda self, _: self.next_port == 1)
      def port_1(self, data):
          self.next_port = 2
          return ActionResult(production=(data, ))
  
      @condition(['token_2'], ['token'])
      @guard(lambda self, _: self.next_port == 2)
      def port_2(self, data):
          self.next_port = 3
          return ActionResult(production=(data, ))
  
      @condition(['token_3'], ['token'])
      @guard(lambda self, _: self.next_port == 3)
      def port_3(self, data):
          self.next_port = 1
          return ActionResult(production=(data, ))
  
      action_priority = (port_1, port_2, port_3)
  
      test_set = [
          {
              'in': {'token_1': [1], 'token_2': ['a'], 'token_3': ['alpha']},
              'out': {'token': [1, 'a', 'alpha']}
          },
          {
              'in': {'token_1': [1]},
              'out': {'token': [1]}
          }
      ]
  
subject: Add Alternate3 actor