def save_file(filepath):
    f = h5py.File(filepath, 'w')
    f.attrs['nb_documents'] = len(self.layers)
    for k, l in enumerate(self.layers):
        g = f.create_group('doc_{}'.format(k))
        weights = l.get_weights()
        g.attrs['nb_params'] = len(weights)
        for n, param in enumerate(weights):
            param_name = 'param_{}'.format(n)
            param_dset = g.create_dataset(param_name, param.shape,
                                          dtype=param.dtype)
            param_dset[:] = param
    f.flush()
    f.close()