More comments

opusparcus.py

@@ -118,7 +118,7 @@ class Opusparcus(datasets.GeneratorBasedBuilder):
             # If there's a common (input, target) tuple from the features,
             # specify them here. They'll be used if as_supervised=True in
             # builder.as_dataset:
-            supervised_keys=(sent1, sent2), # is this correct?
+            supervised_keys=("sent1", "sent2"), # is this correct?
             # Homepage of the dataset for documentation
             homepage=_HOMEPAGE,
             # License for the dataset if available