Update fake_triple_store.py

Author: CaptainOfHacks

tests/fakes/fake_triple_store.py

@@ -1,21 +1,20 @@
 from typing import List, Tuple
 
 import pandas as pd
-from rdflib import URIRef
-
+import rdflib
 from ted_sws.data_manager.adapters.sparql_endpoint import TripleStoreEndpointABC
 
 
 class FakeTripleStoreEndpoint(TripleStoreEndpointABC):
-    def fetch_rdf(self) -> List[Tuple[URIRef, URIRef, URIRef]]:
-        return []
+    def fetch_rdf(self) -> rdflib.Graph:
+        return rdflib.Graph()
 
     def with_query(self, sparql_query: str, substitution_variables: dict = None,
-                   sparql_prefixes: str = "") -> 'TripleStoreEndpointABC':
+                   sparql_prefixes: str = "") -> TripleStoreEndpointABC:
         return self
 
     def with_query_from_file(self, sparql_query_file_path: str, substitution_variables: dict = None,
-                             prefixes: str = "") -> 'TripleStoreEndpointABC':
+                             prefixes: str = "") -> TripleStoreEndpointABC:
         return self
 
     def fetch_tabular(self) -> pd.DataFrame: