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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 history_search_backward(self, e): # ()
        u'''Search backward through the history for the string of characters
        between the start of the current line and the point. This is a
        non-incremental search. By default, this command is unbound.'''
        self.l_buffer=self._history.history_search_backward(self.l_buffer)