old_contents: 
  class Mission(object):
      def __init__(self, sender):
          self.sender = sender
  
      def send(self, message):
          self.sender.send(message)
new_contents: 
  import json
  
  from . import message
  
  class Mission(object):
      def __init__(self, sender):
          self.sender = sender
  
      def send(self, message):
          self.sender.send(message)
  
      def post(self, name, data):
          msg = message.Message({ 'type': 'mission', 'name': name })
          if isinstance(data, dict):
              msg.set_body(json.dumps(data).encode())
          else:
              msg.set_body(data)
          self.sender.send(msg)
  
subject: Add post method