code: def to_flat_dict(self, **kwargs):
          
          if kwargs:
              return self.filter(**kwargs).to_flat_dict()
          return {param.uniquetwig: param for param in self._params}
docs: Convert the :class:`ParameterSet` to a flat dictionary, with keys being
          uniquetwigs to access the parameter and values being the :class:`Parameter`
          objects themselves.
  
          :return: dict of :class:`Parameter`s