code: def full_name(self):
          
          formatted_user = []
          if self.user.first_name is not None:
              formatted_user.append(self.user.first_name)
          if self.user.last_name is not None:
              formatted_user.append(self.user.last_name)
          return " ".join(formatted_user)
docs: Returns the first and last name of the user separated by a space.