code: def get_display_name(self, room=None):
          
          if room:
              try:
                  return room.members_displaynames[self.user_id]
              except KeyError:
                  return self.user_id
          if not self.displayname:
              self.displayname = self.api.get_display_name(self.user_id)
          return self.displayname or self.user_id
docs: Get this user's display name.
  
          Args:
              room (Room): Optional. When specified, return the display name of the user
                  in this room.
  
          Returns:
              The display name. Defaults to the user ID if not set.