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).

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
            )