code: def call_handler(self):
          '''optionally call a handler function'''
          if self.handler is None:
              return
          call = getattr(self.handler, 'call', None)
          if call is not None:
              self.handler_result = call(f call_handler(self):
          '''optionally call a handler function'''
          if self.handler is None:
              return
          call = getattr(self.handler, 'call', None)
          if call is not None:
              self.handler_result = call()
docs: optionally call a handler function