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