fix: validation issues with examples (#2269)

I want to add examples for securing RDFLib network access using
`sys.addaudithook` and `urllib.request.install_opener`, but I want to
also validate the examples in our CI pipeline, so we can demonstrate
they work to our users.

This change adds validation for all examples, and the addition of the
security examples in a seperate PR will then also get validated.

1 files changed, 16 insertions, 10 deletions

diff --git a/examples/custom_eval.py b/examples/custom_eval.py
index 36998087..f8dfd390 100644
--- a/examples/custom_eval.py
+++ b/examples/custom_eval.py
@@ -16,12 +16,19 @@ i.e. in your setup.py::
     }
 """
 
-import rdflib
 
-from rdflib.plugins.sparql.evaluate import evalBGP
+from pathlib import Path
+
+import rdflib
 from rdflib.namespace import FOAF, RDF, RDFS
+from rdflib.plugins.sparql.evaluate import evalBGP
 
-inferredSubClass = RDFS.subClassOf * "*"  # any number of rdfs.subClassOf
+EXAMPLES_DIR = Path(__file__).parent
+
+
+inferred_sub_class = (
+    RDFS.subClassOf * "*"  # type: ignore[operator]
+)  # any number of rdfs.subClassOf
 
 
 def customEval(ctx, part):
@@ -36,7 +43,7 @@ def customEval(ctx, part):
             if t[1] == RDF.type:
                 bnode = rdflib.BNode()
                 triples.append((t[0], t[1], bnode))
-                triples.append((bnode, inferredSubClass, t[2]))
+                triples.append((bnode, inferred_sub_class, t[2]))
             else:
                 triples.append(t)
 
@@ -47,12 +54,11 @@ def customEval(ctx, part):
 
 
 if __name__ == "__main__":
-
     # add function directly, normally we would use setuptools and entry_points
     rdflib.plugins.sparql.CUSTOM_EVALS["exampleEval"] = customEval
 
     g = rdflib.Graph()
-    g.parse("foaf.n3")
+    g.parse(f"{EXAMPLES_DIR / 'foaf.n3'}")
 
     # Add the subClassStmt so that we can query for it!
     g.add((FOAF.Person, RDFS.subClassOf, FOAF.Agent))
@@ -60,11 +66,11 @@ if __name__ == "__main__":
     # Find all FOAF Agents
     for x in g.query(
         f"""
-        PREFIX foaf: <{FOAF}> 
-        
-        SELECT * 
+        PREFIX foaf: <{FOAF}>
+
+        SELECT *
         WHERE {{
-            ?s a foaf:Agent . 
+            ?s a foaf:Agent .
         }}
         """
     ):