code: def iter_genotypes(self):
          
          for info, dosage in self._bgen.iter_variants():
              yield Genotypes(
                  Variant(
                      info.name, CHROM_STR_ENCODE.get(info.chrom, info.chrom),
                      info.pos, [info.a1, info.a2],
                  ),
                  dosage,
                  reference=info.a1,
                  coded=info.a2,
                  multiallelic=True,
              )
docs: Iterates on available markers.
  
          Returns:
              Genotypes instances.