code: def reactToAMQPMessage(message, send_back):
      
      if _instanceof(message, structures.AddUser):
          api.add_user(
              username=message.username,
              password=message.password
          )
          return True
      elif _instanceof(message, structures.RemoveUser):
          api.remove_user(message.username)
          return True
      elif _instanceof(message, structures.ChangePassword):
          api.change_password(
              username=message.username,
              new_password=message.new_password
          )
          return True
      elif _instanceof(message, structures.ListRegisteredUsers):
          return structures.Userlist(api.list_users())
      elif _instanceof(message, structures.SetUserSettings):
          username = message.username
  
          # convert namedtuple to dict (python rocks)
          conf_dict = dict(message._asdict())
          del conf_dict["username"]
  
          passwd_reader.save_user_config(
              username,
              conf_dict
          )
  
          conf_dict = passwd_reader.read_user_config(username)
          conf_dict["username"] = username
          return structures.UserSettings(**conf_dict)
      elif _instanceof(message, structures.GetUserSettings):
          conf_dict = passwd_reader.read_user_config(message.username)
          conf_dict["username"] = message.username
          return structures.UserSettings(**conf_dict)
  
      raise ValueError(
          "Unknown type of request: '" + str(type(message)) + "'!"
      )
docs: React to given (AMQP) message. `message` is expected to be
      :py:func:`collections.namedtuple` structure from :mod:`.structures` filled
      with all necessary data.
  
      Args:
          message (object): One of the request objects defined in
                            :mod:`.structures`.
          send_back (fn reference): Reference to function for responding. This is
                    useful for progress monitoring for example. Function takes
                    one parameter, which may be response structure/namedtuple, or
                    string or whatever would be normally returned.
  
      Returns:
          object: Response class from :mod:`structures`.
  
      Raises:
          ValueError: if bad type of `message` structure is given.