Fix bug in SPARQL intent selection (#8521)

- Description: Fix bug in SPARQL intent selection
- Issue: After the change in #7758 the intent is always set to "UPDATE".
Indeed, if the answer to the prompt contains only "SELECT" the
`find("SELECT")` operation returns a higher value w.r.t. `-1` returned
by `find("UPDATE")`.
- Dependencies: None,
- Tag maintainer: @baskaryan @aditya-29 
- Twitter handle: @mario_scrock

libs/langchain/langchain/chains/graph_qa/sparql.py

@@ -84,17 +84,17 @@ class GraphSparqlQAChain(Chain):
         _intent = self.sparql_intent_chain.run({"prompt": prompt}, callbacks=callbacks)
         intent = _intent.strip()
 
-        if "SELECT" not in intent and "UPDATE" not in intent:
-            raise ValueError(
-                "I am sorry, but this prompt seems to fit none of the currently "
-                "supported SPARQL query types, i.e., SELECT and UPDATE."
-            )
-        elif intent.find("SELECT") < intent.find("UPDATE"):
+        if "SELECT" in intent and "UPDATE" not in intent:
             sparql_generation_chain = self.sparql_generation_select_chain
             intent = "SELECT"
-        else:
+        elif "UPDATE" in intent and "SELECT" not in intent:
             sparql_generation_chain = self.sparql_generation_update_chain
             intent = "UPDATE"
+        else:
+            raise ValueError(
+                "I am sorry, but this prompt seems to fit none of the currently "
+                "supported SPARQL query types, i.e., SELECT and UPDATE."
+            )
 
         _run_manager.on_text("Identified intent:", end="\n", verbose=self.verbose)
         _run_manager.on_text(intent, color="green", end="\n", verbose=self.verbose)