For programmed calls, use these URL query parameters:
id=FBgn0000001,FBgn0000123,... list of IDs
class=gene_region|transcript|translation|3prime_utr|5prime_utr .. sequence class
idclass=FBgn|FBan|DGC|CG .. ID class (optional unless DGC or CG/CT)
mimetype=fasta | genbank | embl | gff .. choice of output format
saveas=file .. save to file