Back compatible: get existing coverage files if they exist

def _get_original_coverage(data, itype="target"):
    """Back compatible: get existing coverage files if they exist
    """
    work_dir = os.path.join(_sv_workdir(data), "raw")
    work_bam = dd.get_work_bam(data) or dd.get_align_bam(data)
    out = []
    base, _ = _bam_to_outbase(work_bam, work_dir, data)
    target_cnn = "%s.targetcoverage.cnn" % base
    anti_cnn = "%s.antitargetcoverage.cnn" % base
    if os.path.exists(target_cnn) and os.path.exists(anti_cnn):
        out.append({"bam": work_bam, "file": target_cnn, "cnntype": "target",
                    "itype": itype, "sample": dd.get_sample_name(data)})
        out.append({"bam": work_bam, "file": anti_cnn, "cnntype": "antitarget",
                    "itype": itype, "sample": dd.get_sample_name(data)})
    return out