code: def expand(self, *relationships):
          
  
          for relationship in relationships:
              if relationship == 'event':
                  relationship = '{}/event'.format(self.protocol.get_service_keyword('event_message_type'))
              self._expands.add(relationship)
  
          return self
docs: Adds the relationships (e.g. "event" or "attachments")
          that should be expanded with the $expand parameter
          Important: The ApiComponent using this should know how to handle this relationships.
              eg: Message knows how to handle attachments, and event (if it's an EventMessage).
          Important: When using expand on multi-value relationships a max of 20 items will be returned.
          :param str relationships: the relationships tuple to expand.
          :rtype: Query