langchain[patch]: return formatted SPARQL query on demand (#11263)

- **Description:** Added the `return_sparql_query` feature to the
`GraphSparqlQAChain` class, allowing users to get the formatted SPARQL
query along with the chain's result.
  - **Issue:** NA
  - **Dependencies:** None

Note: I've ensured that the PR passes linting and testing by running
make format, make lint, and make test locally.

I have added a test for the integration (which relies on network access)
and I have added an example to the notebook showing its use.

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

@@ -41,15 +41,25 @@ class GraphSparqlQAChain(Chain):
     sparql_generation_update_chain: LLMChain
     sparql_intent_chain: LLMChain
     qa_chain: LLMChain
+    return_sparql_query: bool = False
     input_key: str = "query"  #: :meta private:
     output_key: str = "result"  #: :meta private:
+    sparql_query_key: str = "sparql_query"  #: :meta private:
 
     @property
     def input_keys(self) -> List[str]:
+        """Return the input keys.
+
+        :meta private:
+        """
         return [self.input_key]
 
     @property
     def output_keys(self) -> List[str]:
+        """Return the output keys.
+
+        :meta private:
+        """
         _output_keys = [self.output_key]
         return _output_keys
 
@@ -135,4 +145,8 @@ class GraphSparqlQAChain(Chain):
             res = "Successfully inserted triples into the graph."
         else:
             raise ValueError("Unsupported SPARQL query type.")
-        return {self.output_key: res}
+
+        chain_result: Dict[str, Any] = {self.output_key: res}
+        if self.return_sparql_query:
+            chain_result[self.sparql_query_key] = generated_sparql
+        return chain_result

libs/langchain/tests/integration_tests/chains/test_graph_database_sparql.py

@@ -78,3 +78,29 @@ def test_sparql_insert() -> None:
         os.remove(_local_copy)
     except OSError:
         pass
+
+
+def test_sparql_select_return_query() -> None:
+    """
+    Test for generating and executing simple SPARQL SELECT query
+    and returning the generated SPARQL query.
+    """
+    berners_lee_card = "http://www.w3.org/People/Berners-Lee/card"
+
+    graph = RdfGraph(
+        source_file=berners_lee_card,
+        standard="rdf",
+    )
+
+    chain = GraphSparqlQAChain.from_llm(
+        OpenAI(temperature=0), graph=graph, return_sparql_query=True
+    )
+    output = chain("What is Tim Berners-Lee's work homepage?")
+
+    # Verify the expected answer
+    expected_output = (
+        " The work homepage of Tim Berners-Lee is "
+        "http://www.w3.org/People/Berners-Lee/."
+    )
+    assert output["result"] == expected_output
+    assert "sparql_query" in output