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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 parse(self, input):
 """ Parses a time delta from the input. See :py:class:`TimeDeltaParameter` for details on supported formats. """

        result = self._parseIso8601(input)
        if not result:
            result = self._parseSimple(input)
        if result is not None:
            return result
        else:
            raise ParameterException("Invalid time delta - could not parse %s" % input)