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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 _descr_str(descr, data, region):
 """Add additional useful information from data to description string. """

    if data:
        name = dd.get_sample_name(data)
        if name:
            descr = "{0} : {1}".format(descr, name)
        elif "work_bam" in data:
            descr = "{0} : {1}".format(descr, os.path.basename(data["work_bam"]))
    if region:
        descr = "{0} : {1}".format(descr, region)
    return descr