Save model

        Parameters
        ----------
        filename : str
            path to model file

def save_parameters(self, filename):
        """Save model

        Parameters
        ----------
        filename : str
            path to model file
        """
        params = self._collect_params_with_prefix()
        if self.pret_word_embs:  # don't save word embeddings inside model
            params.pop('pret_word_embs.weight', None)
        arg_dict = {key: val._reduce() for key, val in params.items()}
        ndarray.save(filename, arg_dict)