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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 _get_signal_handler(self, handler):
 """ get the callback function for handler If the handler is None, returns signal.SIG_IGN. If the handler is a string, return the matching attribute of this instance if possible. Else return the handler itself. :param handler: :type handler: str, None, function :return: function """

        if not handler:
            result = signal.SIG_IGN
        elif isinstance(handler, string_types):
            result = getattr(self, handler)
        else:
            result = handler
        return result