Fix incomplete typing

Author: mielvds

lib/pyld/jsonld.py

@@ -986,7 +986,7 @@ def normalize(self, input_, options):
                 {'format': cause.format}) from cause
 
 
-    def from_rdf(self, dataset: dict | Dataset, options):
+    def from_rdf(self, dataset: dict | Dataset | str, options):
         """
         Converts an RDF dataset to JSON-LD.