Parse command line arguments.

def parse_args():
    """Parse command line arguments."""
    parser = argparse.ArgumentParser(
        description='Text Classification with FastText',
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)

    # Computation options
    group = parser.add_argument_group('Computation arguments')
    group.add_argument('--input', type=str, help='Input file location')
    group.add_argument(
        '--validation', type=str, help='Validation file Location ')
    group.add_argument(
        '--output', type=str, help='Location to save trained model')
    group.add_argument(
        '--ngrams', type=int, default=1, help='NGrams used for training')
    group.add_argument(
        '--batch_size', type=int, default=16, help='Batch size for training.')
    group.add_argument('--epochs', type=int, default=10, help='Epoch limit')
    group.add_argument(
        '--gpu',
        type=int,
        help=('Number (index) of GPU to run on, e.g. 0. '
              'If not specified, uses CPU.'))
    group.add_argument(
        '--no-hybridize',
        action='store_true',
        help='Disable hybridization of gluon HybridBlocks.')

    # Model
    group = parser.add_argument_group('Model arguments')
    group.add_argument(
        '--emsize', type=int, default=100, help='Size of embedding vectors.')

    # Optimization options
    group = parser.add_argument_group('Optimization arguments')
    group.add_argument('--optimizer', type=str, default='adam')
    group.add_argument('--lr', type=float, default=0.05)

    args = parser.parse_args()
    return args