community[minor], langchian[minor]: Add Neptune Rdf graph and chain (#16650)

**Description**: This PR adds a chain for Amazon Neptune graph database
RDF format. It complements the existing Neptune Cypher chain. The PR
also includes a Neptune RDF graph class to connect to, introspect, and
query a Neptune RDF graph database from the chain. A sample notebook is
provided under docs that demonstrates the overall effect: invoking the
chain to make natural language queries against Neptune using an LLM.

**Issue**: This is a new feature
 
**Dependencies**: The RDF graph class depends on the AWS boto3 library
if using IAM authentication to connect to the Neptune database.

---------

Co-authored-by: Piyush Jain <piyushjain@duck.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/langchain/langchain/chains/__init__.py

@@ -41,6 +41,7 @@ from langchain.chains.graph_qa.hugegraph import HugeGraphQAChain
 from langchain.chains.graph_qa.kuzu import KuzuQAChain
 from langchain.chains.graph_qa.nebulagraph import NebulaGraphQAChain
 from langchain.chains.graph_qa.neptune_cypher import NeptuneOpenCypherQAChain
+from langchain.chains.graph_qa.neptune_sparql import NeptuneSparqlQAChain
 from langchain.chains.graph_qa.ontotext_graphdb import OntotextGraphDBQAChain
 from langchain.chains.graph_qa.sparql import GraphSparqlQAChain
 from langchain.chains.history_aware_retriever import create_history_aware_retriever
@@ -116,6 +117,7 @@ __all__ = [
     "NatBotChain",
     "NebulaGraphQAChain",
     "NeptuneOpenCypherQAChain",
+    "NeptuneSparqlQAChain",
     "OpenAIModerationChain",
     "OpenAPIEndpointChain",
     "QAGenerationChain",

libs/langchain/langchain/chains/graph_qa/neptune_sparql.py

@@ -0,0 +1,196 @@
+"""
+Question answering over an RDF or OWL graph using SPARQL.
+"""
+from __future__ import annotations
+
+from typing import Any, Dict, List, Optional
+
+from langchain_community.graphs import NeptuneRdfGraph
+from langchain_core.language_models import BaseLanguageModel
+from langchain_core.prompts.base import BasePromptTemplate
+from langchain_core.prompts.prompt import PromptTemplate
+from langchain_core.pydantic_v1 import Field
+
+from langchain.callbacks.manager import CallbackManagerForChainRun
+from langchain.chains.base import Chain
+from langchain.chains.graph_qa.prompts import SPARQL_QA_PROMPT
+from langchain.chains.llm import LLMChain
+
+INTERMEDIATE_STEPS_KEY = "intermediate_steps"
+
+SPARQL_GENERATION_TEMPLATE = """
+Task: Generate a SPARQL SELECT statement for querying a graph database.
+For instance, to find all email addresses of John Doe, the following 
+query in backticks would be suitable:
+```
+PREFIX foaf: <http://xmlns.com/foaf/0.1/>
+SELECT ?email
+WHERE {{
+    ?person foaf:name "John Doe" .
+    ?person foaf:mbox ?email .
+}}
+```
+Instructions:
+Use only the node types and properties provided in the schema.
+Do not use any node types and properties that are not explicitly provided.
+Include all necessary prefixes.
+
+Examples:
+
+Schema:
+{schema}
+Note: Be as concise as possible.
+Do not include any explanations or apologies in your responses.
+Do not respond to any questions that ask for anything else than 
+for you to construct a SPARQL query.
+Do not include any text except the SPARQL query generated.
+
+The question is:
+{prompt}"""
+
+SPARQL_GENERATION_PROMPT = PromptTemplate(
+    input_variables=["schema", "prompt"], template=SPARQL_GENERATION_TEMPLATE
+)
+
+
+def extract_sparql(query: str) -> str:
+    query = query.strip()
+    querytoks = query.split("```")
+    if len(querytoks) == 3:
+        query = querytoks[1]
+
+        if query.startswith("sparql"):
+            query = query[6:]
+    elif query.startswith("<sparql>") and query.endswith("</sparql>"):
+        query = query[8:-9]
+    return query
+
+
+class NeptuneSparqlQAChain(Chain):
+    """Chain for question-answering against a Neptune graph
+    by generating SPARQL statements.
+
+    *Security note*: Make sure that the database connection uses credentials
+        that are narrowly-scoped to only include necessary permissions.
+        Failure to do so may result in data corruption or loss, since the calling
+        code may attempt commands that would result in deletion, mutation
+        of data if appropriately prompted or reading sensitive data if such
+        data is present in the database.
+        The best way to guard against such negative outcomes is to (as appropriate)
+        limit the permissions granted to the credentials used with this tool.
+
+        See https://python.langchain.com/docs/security for more information.
+
+    Example:
+        .. code-block:: python
+
+        chain = NeptuneSparqlQAChain.from_llm(
+            llm=llm,
+            graph=graph
+        )
+        response = chain.invoke(query)
+    """
+
+    graph: NeptuneRdfGraph = Field(exclude=True)
+    sparql_generation_chain: LLMChain
+    qa_chain: LLMChain
+    input_key: str = "query"  #: :meta private:
+    output_key: str = "result"  #: :meta private:
+    top_k: int = 10
+    return_intermediate_steps: bool = False
+    """Whether or not to return the intermediate steps along with the final answer."""
+    return_direct: bool = False
+    """Whether or not to return the result of querying the graph directly."""
+    extra_instructions: Optional[str] = None
+    """Extra instructions by the appended to the query generation prompt."""
+
+    @property
+    def input_keys(self) -> List[str]:
+        return [self.input_key]
+
+    @property
+    def output_keys(self) -> List[str]:
+        _output_keys = [self.output_key]
+        return _output_keys
+
+    @classmethod
+    def from_llm(
+        cls,
+        llm: BaseLanguageModel,
+        *,
+        qa_prompt: BasePromptTemplate = SPARQL_QA_PROMPT,
+        sparql_prompt: BasePromptTemplate = SPARQL_GENERATION_PROMPT,
+        examples: Optional[str] = None,
+        **kwargs: Any,
+    ) -> NeptuneSparqlQAChain:
+        """Initialize from LLM."""
+        qa_chain = LLMChain(llm=llm, prompt=qa_prompt)
+        template_to_use = SPARQL_GENERATION_TEMPLATE
+        if examples:
+            template_to_use = template_to_use.replace(
+                "Examples:", "Examples: " + examples
+            )
+            sparql_prompt = PromptTemplate(
+                input_variables=["schema", "prompt"], template=template_to_use
+            )
+        sparql_generation_chain = LLMChain(llm=llm, prompt=sparql_prompt)
+
+        return cls(
+            qa_chain=qa_chain,
+            sparql_generation_chain=sparql_generation_chain,
+            examples=examples,
+            **kwargs,
+        )
+
+    def _call(
+        self,
+        inputs: Dict[str, Any],
+        run_manager: Optional[CallbackManagerForChainRun] = None,
+    ) -> Dict[str, str]:
+        """
+        Generate SPARQL query, use it to retrieve a response from the gdb and answer
+        the question.
+        """
+        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
+        callbacks = _run_manager.get_child()
+        prompt = inputs[self.input_key]
+
+        intermediate_steps: List = []
+
+        generated_sparql = self.sparql_generation_chain.run(
+            {"prompt": prompt, "schema": self.graph.get_schema}, callbacks=callbacks
+        )
+
+        # Extract SPARQL
+        generated_sparql = extract_sparql(generated_sparql)
+
+        _run_manager.on_text("Generated SPARQL:", end="\n", verbose=self.verbose)
+        _run_manager.on_text(
+            generated_sparql, color="green", end="\n", verbose=self.verbose
+        )
+
+        intermediate_steps.append({"query": generated_sparql})
+
+        context = self.graph.query(generated_sparql)
+
+        if self.return_direct:
+            final_result = context
+        else:
+            _run_manager.on_text("Full Context:", end="\n", verbose=self.verbose)
+            _run_manager.on_text(
+                str(context), color="green", end="\n", verbose=self.verbose
+            )
+
+            intermediate_steps.append({"context": context})
+
+            result = self.qa_chain(
+                {"prompt": prompt, "context": context},
+                callbacks=callbacks,
+            )
+            final_result = result[self.qa_chain.output_key]
+
+        chain_result: Dict[str, Any] = {self.output_key: final_result}
+        if self.return_intermediate_steps:
+            chain_result[INTERMEDIATE_STEPS_KEY] = intermediate_steps
+
+        return chain_result

libs/langchain/tests/unit_tests/chains/test_imports.py

@@ -33,6 +33,7 @@ EXPECTED_ALL = [
     "NatBotChain",
     "NebulaGraphQAChain",
     "NeptuneOpenCypherQAChain",
+    "NeptuneSparqlQAChain",
     "OpenAIModerationChain",
     "OpenAPIEndpointChain",
     "QAGenerationChain",