IMPROVEMENT Neptune graph updates (#13491)

## Description
This PR adds an option to allow unsigned requests to the Neptune
database when using the `NeptuneGraph` class.

```python
graph = NeptuneGraph(
    host='<my-cluster>',
    port=8182,
    sign=False
)
```

Also, added is an option in the `NeptuneOpenCypherQAChain` to provide
additional domain instructions to the graph query generation prompt.
This will be injected in the prompt as-is, so you should include any
provider specific tags, for example `<instructions>` or `<INSTR>`.

```python
chain = NeptuneOpenCypherQAChain.from_llm(
    llm=llm,
    graph=graph,
    extra_instructions="""
    Follow these instructions to build the query:
    1. Countries contain airports, not the other way around
    2. Use the airport code for identifying airports
    """
)
```

libs/langchain/langchain/chains/graph_qa/neptune_cypher.py

@@ -116,6 +116,8 @@ class NeptuneOpenCypherQAChain(Chain):
     """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]:
@@ -141,6 +143,7 @@ class NeptuneOpenCypherQAChain(Chain):
         *,
         qa_prompt: BasePromptTemplate = CYPHER_QA_PROMPT,
         cypher_prompt: Optional[BasePromptTemplate] = None,
+        extra_instructions: Optional[str] = None,
         **kwargs: Any,
     ) -> NeptuneOpenCypherQAChain:
         """Initialize from LLM."""
@@ -152,6 +155,7 @@ class NeptuneOpenCypherQAChain(Chain):
         return cls(
             qa_chain=qa_chain,
             cypher_generation_chain=cypher_generation_chain,
+            extra_instructions=extra_instructions,
             **kwargs,
         )
 
@@ -168,7 +172,12 @@ class NeptuneOpenCypherQAChain(Chain):
         intermediate_steps: List = []
 
         generated_cypher = self.cypher_generation_chain.run(
-            {"question": question, "schema": self.graph.get_schema}, callbacks=callbacks
+            {
+                "question": question,
+                "schema": self.graph.get_schema,
+                "extra_instructions": self.extra_instructions or "",
+            },
+            callbacks=callbacks,
         )
 
         # Extract Cypher code if it is wrapped in backticks

libs/langchain/langchain/chains/graph_qa/prompts.py

@@ -320,7 +320,7 @@ Instructions:
 Generate the query in openCypher format and follow these rules:
 Do not use `NONE`, `ALL` or `ANY` predicate functions, rather use list comprehensions.
 Do not use `REDUCE` function. Rather use a combination of list comprehension and the `UNWIND` clause to achieve similar results.
-Do not use `FOREACH` clause. Rather use a combination of `WITH` and `UNWIND` clauses to achieve similar results.
+Do not use `FOREACH` clause. Rather use a combination of `WITH` and `UNWIND` clauses to achieve similar results.{extra_instructions}
 \n"""
 
 NEPTUNE_OPENCYPHER_GENERATION_TEMPLATE = CYPHER_GENERATION_TEMPLATE.replace(
@@ -328,18 +328,18 @@ NEPTUNE_OPENCYPHER_GENERATION_TEMPLATE = CYPHER_GENERATION_TEMPLATE.replace(
 )
 
 NEPTUNE_OPENCYPHER_GENERATION_PROMPT = PromptTemplate(
-    input_variables=["schema", "question"],
+    input_variables=["schema", "question", "extra_instructions"],
     template=NEPTUNE_OPENCYPHER_GENERATION_TEMPLATE,
 )
 
 NEPTUNE_OPENCYPHER_GENERATION_SIMPLE_TEMPLATE = """
-Write an openCypher query to answer the following question. Do not explain the answer. Only return the query. 
+Write an openCypher query to answer the following question. Do not explain the answer. Only return the query.{extra_instructions}
 Question:  "{question}". 
 Here is the property graph schema: 
 {schema}
 \n"""
 
 NEPTUNE_OPENCYPHER_GENERATION_SIMPLE_PROMPT = PromptTemplate(
-    input_variables=["schema", "question"],
+    input_variables=["schema", "question", "extra_instructions"],
     template=NEPTUNE_OPENCYPHER_GENERATION_SIMPLE_TEMPLATE,
 )

libs/langchain/langchain/graphs/neptune_graph.py

@@ -30,6 +30,7 @@ class NeptuneGraph:
         credentials_profile_name: optional AWS profile name
         region_name: optional AWS region, e.g., us-west-2
         service: optional service name, default is neptunedata
+        sign: optional, whether to sign the request payload, default is True
 
     Example:
         .. code-block:: python
@@ -60,6 +61,7 @@ class NeptuneGraph:
         credentials_profile_name: Optional[str] = None,
         region_name: Optional[str] = None,
         service: str = "neptunedata",
+        sign: bool = True,
     ) -> None:
         """Create a new Neptune graph wrapper instance."""
 
@@ -83,7 +85,17 @@ class NeptuneGraph:
 
                 client_params["endpoint_url"] = f"{protocol}://{host}:{port}"
 
-                self.client = session.client(service, **client_params)
+                if sign:
+                    self.client = session.client(service, **client_params)
+                else:
+                    from botocore import UNSIGNED
+                    from botocore.config import Config
+
+                    self.client = session.client(
+                        service,
+                        **client_params,
+                        config=Config(signature_version=UNSIGNED),
+                    )
 
         except ImportError:
             raise ModuleNotFoundError(
@@ -120,7 +132,15 @@ class NeptuneGraph:
 
     def query(self, query: str, params: dict = {}) -> Dict[str, Any]:
         """Query Neptune database."""
-        return self.client.execute_open_cypher_query(openCypherQuery=query)
+        try:
+            return self.client.execute_open_cypher_query(openCypherQuery=query)
+        except Exception as e:
+            raise NeptuneQueryException(
+                {
+                    "message": "An error occurred while executing the query.",
+                    "details": str(e),
+                }
+            )
 
     def _get_summary(self) -> Dict:
         try: