Add syntaxis "," needed

BLURB.py

@@ -102,7 +102,7 @@ class Blurb(datasets.GeneratorBasedBuilder):
   BUILDER_CONFIGS = [
     BlurbConfig(name='BC5CDR-chem-IOB', task='ner', label_classes=['O', 'B-Chemical', 'I-Chemical'],
                     version=datasets.Version(_VERSION),
-                    data_url = "https://github.com/cambridgeltl/MTL-Bioinformatics-2016/tree/master/data/"
+                    data_url = "https://github.com/cambridgeltl/MTL-Bioinformatics-2016/tree/master/data/",
                     description='BC5-CHEM',
                     citation=CITATION_BC5_CHEM)
   ]