code: def get_parameters_at_instant(self, instant):
          
          if isinstance(instant, periods.Period):
              instant = instant.start
          elif isinstance(instant, (str, int)):
              instant = periods.instant(instant)
          else:
              assert isinstance(instant, periods.Instant), "Expected an Instant (e.g. Instant((2017, 1, 1)) ). Got: {}.".format(instant)
  
          parameters_at_instant = self._parameters_at_instant_cache.get(instant)
          if parameters_at_instant is None and self.parameters is not None:
              parameters_at_instant = self.parameters.get_at_instant(str(instant))
              self._parameters_at_instant_cache[instant] = parameters_at_instant
          return parameters_at_instant
docs: Get the parameters of the legislation at a given instant
  
          :param instant: string of the format 'YYYY-MM-DD' or `openfisca_core.periods.Instant` instance.
          :returns: The parameters of the legislation at a given instant.
          :rtype: :any:`ParameterNodeAtInstant`