docs: def iter_genotypes(self):
          """Iterates on available markers.
  
          Returns:
              Genotypes instances.
  
          Note
          ====
              If the sample IDs are not unique, the index is changed to be the
              sample family ID and individual ID (i.e. fid_iid).
  
          """
          # Iterating over all markers
          for i, (_, genotypes) in enumerate(self.bed.iter_geno()):
              info = self.bim.iloc[i, :]
  
              yield Genotypes(
                  Variant(info.name, CHROM_INT_TO_STR[info.chrom],
                          info.pos, [info.a1, info.a2]),
                  self._normalize_missing(genotypes),
                  reference=info.a2,
                  coded=info.a1,
                  multiallelic=info.multiallelic
              )