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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 _read_cnv_ssms(in_file):
 """Map CNVs to associated SSMs """

    out = {}
    with open(in_file) as in_handle:
        in_handle.readline()  # header
        for line in in_handle:
            parts = line.strip().split()
            if len(parts) > 3:
                cnvid, _, _, ssms = parts
                out[cnvid] = [x.split(",")[0] for x in ssms.split(";")]
    return out