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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 combine_bam(in_files, out_file, config):
 """Parallel target to combine multiple BAM files. """

    runner = broad.runner_from_path("picard", config)
    runner.run_fn("picard_merge", in_files, out_file)
    for in_file in in_files:
        save_diskspace(in_file, "Merged into {0}".format(out_file), config)
    bam.index(out_file, config)
    return out_file