Iterates on available markers.

        Returns:
            Genotypes instances.

def iter_genotypes(self):
        """Iterates on available markers.

        Returns:
            Genotypes instances.

        """
        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,
            )