feat: Check for JSON result format to get_bindings_from_query_result

The default return format for SPARQLWrapper is XML, since the format
option cannot be set from an already retrieved QueryResult set and the
function depends on JSON results, raise an error if the set result
format is not JSON.

rdfproxy/utils/utils.py

@@ -10,6 +10,12 @@
 
 def get_bindings_from_query_result(query_result: QueryResult) -> Iterator[dict]:
     """Extract just the bindings from a SPARQLWrapper.QueryResult."""
+    if (result_format := query_result.requestedFormat) != "json":
+        raise Exception(
+            "Only QueryResult objects with JSON format are currently supported. "
+            f"Received object with requestedFormat '{result_format}'."
+        )
+
     query_json = cast(Mapping, query_result.convert())
     bindings = map(
         lambda binding: valmap(lambda v: v["value"], binding),