'Lookup the :class:`Param` instance that this :class:``PARAMref``
references.'

def get_ref(self):

    for param in self._table._votable.iter_fields_and_params():
        if (isinstance(param, Param) and (param.ID == self.ref)):
            return param
    vo_raise(u"No    params    named    '{}'".format(self.ref), self._config, self._pos, KeyError)
