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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def compute_lengths(sequence_data: mx.sym.Symbol) -> mx.sym.Symbol: """ Computes sequence lengths of PAD_ID-padded data in sequence_data. :param sequence_data: Input data. Shape: (batch_size, seq_len). :return: Length data. Shape: (batch_size,). """

    return mx.sym.sum(sequence_data != C.PAD_ID, axis=1)