docs: def get_variants_in_region(self, chrom, start, end):
          """Iterate over variants in a region."""
          if not self.has_index:
              raise NotImplementedError("Not implemented when IMPUTE2 file is "
                                        "not indexed (see genipe)")
  
          if not self._index_has_location:
              raise NotImplementedError("Not implemented when index doesn't "
                                        "have location information.")
  
          # Getting the required variants
          required = self._impute2_index.loc[
              (self._impute2_index.chrom == CHROM_STR_TO_INT[chrom]) &
              (start <= self._impute2_index.pos) &
              (self._impute2_index.pos <= end)
          ]
  
          for name, variant_info in required.iterrows():
              for genotypes in self.get_variant_by_name(name, variant_info):
                  self._fix_genotypes_object(genotypes, variant_info)
                  yield genotypes