Line 3756: should be attrs instead of attr

Current: if self.classes.issubset(set([s.lower() for s in e.attr.get("class", [])])) is False:

Should be: if self.classes.issubset(set([s.lower() for s in e.attrs.get("class", [])])) is False:

Note: This change makes sense in python2 pattern. pattern3 should probably be e.attributes