def METHOD_NAME(self, output_flipped, matched_parts):
    assert output_flipped.ndim == 4,\
            'output_flipped should be [batch_size, num_joints, height, width]'
    output_flipped = output_flipped[:, :, :, ::-1]
    for pair in matched_parts:
        tmp = output_flipped[:, pair[0], :, :].copy()
        output_flipped[:, pair[0], :, :] = output_flipped[:, pair[1], :, :]
        output_flipped[:, pair[1], :, :] = tmp
    return output_flipped