Print tab-separated table headers

def prt_tsv_hdr(prt, data_nts, **kws):
    """Print tab-separated table headers"""
    sep = "\t" if 'sep' not in kws else kws['sep']
    flds_all = data_nts[0]._fields
    hdrs = get_hdrs(flds_all, **kws)
    prt.write("# {}\n".format(sep.join(hdrs)))