code: def _get_other_allele_by_zygosity(allele_id, zygosity):
          
          other_allele = None
          if zygosity == 'homozygous':
              other_allele = allele_id
          elif zygosity == 'hemizygous':
              other_allele = '0'
          elif zygosity == 'unknown':  # we'll use this as a convention
              other_allele = '?'
          elif zygosity == 'complex':  # transgenics
              other_allele = '0'
          elif zygosity == 'heterozygous':
              # passing on hets until a different fxn
              pass
          else:
              LOG.warning("Unconfigured zygosity: %s", zygosity)
  
          return other_allele
docs: A helper function to switch on the zygosity,
          and return the appropriate allele id, or symbol.
          :param allele_id:
          :param zygosity:
          :return: