external gene names cannot be used as filter

[ChelseaCHENX]

Hi, I was trying dataset.query(attributes=['ensembl_gene_id', 'external_gene_name', 'description'], filters={'external_gene_name': ['PTEN']}) when an error pops out: BiomartException: Unknown filter external_gene_name, check dataset filters for a list of valid filters. Not sure if this can be added as a filter? Thx!