Hi, it seems that the tutorial (https://bioservices.readthedocs.io/en/latest/biomart.html) uses this syntax to pass a list to the filter:

queries = ["", ""]
b.add_filter_to_xml("ensemble_gene_id", queries)

Although, it does not work on my end, but it does if I change the input for

queries = ["", ""]
b.add_filter_to_xml("ensemble_gene_id", ",".join(queries))

This could either be modified in the code (more elegant) or the tutorial could be modified.

Thanks,