code: def _is_possible_loh(rec, vcf_rec, params, somatic_info, use_status=False, max_normal_depth=None):
      
      if _is_biallelic_snp(rec) and _passes_plus_germline(rec, use_status=use_status):
          stats = _tumor_normal_stats(rec, somatic_info, vcf_rec)
          depths = [tz.get_in([x, "depth"], stats) for x in ["normal", "tumor"]]
          depths = [d for d in depths if d is not None]
          normal_freq = tz.get_in(["normal", "freq"], stats)
          tumor_freq = tz.get_in(["tumor", "freq"], stats)
          if all([d > params["min_depth"] for d in depths]):
              if max_normal_depth and tz.get_in(["normal", "depth"], stats, 0) > max_normal_depth:
                  return None
              if normal_freq is not None:
                  if normal_freq >= params["min_freq"] and normal_freq <= params["max_freq"]:
                      return stats
              elif (tumor_freq >= params["tumor_only"]["min_freq"] and
                      tumor_freq <= params["tumor_only"]["max_freq"]):
                  if (vcf_rec and not _has_population_germline(vcf_rec)) or is_population_germline(rec):
                      return stats
docs: Check if the VCF record is a het in the normal with sufficient support.
  
      Only returns SNPs, since indels tend to have less precise frequency measurements.