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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 ck2respth(argv=None):
 """Command-line entry point for converting a ChemKED YAML file to a ReSpecTh XML file. """

    parser = ArgumentParser(
        description='Convert a ChemKED YAML file to a ReSpecTh XML file.'
        )
    parser.add_argument('-i', '--input',
                        type=str,
                        required=True,
                        help='Input filename (e.g., "file1.xml")'
                        )
    parser.add_argument('-o', '--output',
                        type=str,
                        required=False,
                        default='',
                        help='Output filename (e.g., "file1.yaml")'
                        )

    args = parser.parse_args(argv)

    c = chemked.ChemKED(yaml_file=args.input)
    c.convert_to_ReSpecTh(args.output)