I'm trying to implement a function to convert Ensembl chromosome names to UCSC names for many potential input species (i.e. the intersection of species supported by both sources). I saw the `seqlevelStyles` function in GenomeInfoDb, but only the canonical chromosomes are mapped. Why is that? It's kind of funny because the canonical ones can mostly be fixed with a `sub()` call. It's the patches that are really irregular and vexing.