def data_to_dict(self, sysbase=False):
        """
        Return the loaded model parameters as one dictionary.

        Each key of the dictionary is a parameter name, and the value is a
        list of all the parameter values.

        :param sysbase: use system base quantities
        :type sysbase: bool
        """
        assert isinstance(sysbase, bool)

        ret = {}

        for key in self.data_keys:
            if (not sysbase) and (key in self._store):
                val = self._store[key]
            else:
                val = self.__dict__[key]

            ret[key] = val

        return ret