Retrieve evidence BAM for the sample if it exists

def _get_evidence_bam(work_dir, data):
    """Retrieve evidence BAM for the sample if it exists
    """
    evidence_bam = glob.glob(os.path.join(work_dir, "results", "evidence",
                                            "evidence_*.%s*.bam" % (dd.get_sample_name(data))))
    if evidence_bam:
        return evidence_bam[0]