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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _call_handler(self, key, insert_text):
 """ Callback to handler. """

        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))