Parses a time delta from the input.

        See :py:class:`TimeDeltaParameter` for details on supported formats.

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)