code: def _call_handler(self, key, insert_text):
          
          if isinstance(key, tuple):
              for k in key:
                  self._call_handler(k, insert_text)
          else:
              if key == Keys.BracketedPaste:
                  self._in_bracketed_paste = True
                  self._paste_buffer = ''
              else:
                  self.feed_key_callback(KeyPress(key, insert_text))
docs: Callback to handler.