Genome features doesn't seem to find genes in `Af1`

For some reason, `api.genome_features(region=contig).query("type == api._gff_gene_type")` doesn't find any gene for `api == af1` in `test_genomes_features.py`. Somewhere else in the same file `api.genome_features(region=contig).query("type == 'gene'")` is used even for `api == af1`, which shouldn't return anything (but absence of genes is handled differently in this case).