def selectMaxCDS(trans):
    """select transcript with max CDS length
  """
    maxlen, mt = 0, None
    for t in trans:
        cds1, cds2 = t.cds_start(cdna=True), t.cds_stop(cdna=True)
        try:
            cdslen = cds2 - cds1
        except:
            continue
        if cdslen % 3 != 0:
            continue
        if cdslen > maxlen:
            maxlen, mt = cdslen, t
    return mt
