Add Graph interface (#11012)

Replace this entire comment with:
  - **Description:** Add a Graph interface
  - **Tag maintainer:** @baskaryan @hwchase17 
  - **Twitter handle:** @g_korland

libs/langchain/langchain/chains/graph_qa/cypher.py

@@ -9,7 +9,7 @@ from langchain.chains.base import Chain
 from langchain.chains.graph_qa.cypher_utils import CypherQueryCorrector, Schema
 from langchain.chains.graph_qa.prompts import CYPHER_GENERATION_PROMPT, CYPHER_QA_PROMPT
 from langchain.chains.llm import LLMChain
-from langchain.graphs.neo4j_graph import Neo4jGraph
+from langchain.graphs.graph_store import GraphStore
 from langchain.pydantic_v1 import Field
 from langchain.schema import BasePromptTemplate
 from langchain.schema.language_model import BaseLanguageModel
@@ -79,7 +79,7 @@ def construct_schema(
 class GraphCypherQAChain(Chain):
     """Chain for question-answering against a graph by generating Cypher statements."""
 
-    graph: Neo4jGraph = Field(exclude=True)
+    graph: GraphStore = Field(exclude=True)
     cypher_generation_chain: LLMChain
     qa_chain: LLMChain
     graph_schema: str
@@ -151,7 +151,7 @@ class GraphCypherQAChain(Chain):
             )
 
         graph_schema = construct_schema(
-            kwargs["graph"].structured_schema, include_types, exclude_types
+            kwargs["graph"].get_structured_schema, include_types, exclude_types
         )
 
         cypher_query_corrector = None

libs/langchain/langchain/graphs/falkordb_graph.py

@@ -1,7 +1,7 @@
 from typing import Any, Dict, List
 
 from langchain.graphs.graph_document import GraphDocument
-from langchain.graphs.neo4j_graph import Neo4jGraph
+from langchain.graphs.graph_store import GraphStore
 
 node_properties_query = """
 MATCH (n)
@@ -32,7 +32,7 @@ RETURN DISTINCT {start: src_label, type: rel_type, end: dst_label} AS output
 """
 
 
-class FalkorDBGraph(Neo4jGraph):
+class FalkorDBGraph(GraphStore):
     """FalkorDB wrapper for graph operations.
 
     *Security note*: Make sure that the database connection uses credentials
@@ -58,8 +58,8 @@ class FalkorDBGraph(Neo4jGraph):
                 "Please install it with `pip install redis`."
             )
 
-        driver = redis.Redis(host=host, port=port)
+        self._driver = redis.Redis(host=host, port=port)
-        self._graph = Graph(driver, database)
+        self._graph = Graph(self._driver, database)
         self.schema: str = ""
         self.structured_schema: Dict[str, Any] = {}
 

libs/langchain/langchain/graphs/graph_store.py

@@ -0,0 +1,37 @@
+from abc import abstractmethod
+from typing import Any, Dict, List
+
+from langchain.graphs.graph_document import GraphDocument
+
+
+class GraphStore:
+    """An abstract class wrapper for graph operations."""
+
+    @property
+    @abstractmethod
+    def get_schema(self) -> str:
+        """Returns the schema of the Graph database"""
+        pass
+
+    @property
+    @abstractmethod
+    def get_structured_schema(self) -> Dict[str, Any]:
+        """Returns the schema of the Graph database"""
+        pass
+
+    @abstractmethod
+    def query(self, query: str, params: dict = {}) -> List[Dict[str, Any]]:
+        """Query the graph."""
+        pass
+
+    @abstractmethod
+    def refresh_schema(self) -> None:
+        """Refreshes the graph schema information."""
+        pass
+
+    @abstractmethod
+    def add_graph_documents(
+        self, graph_documents: List[GraphDocument], include_source: bool = False
+    ) -> None:
+        """Take GraphDocument as input as uses it to construct a graph."""
+        pass

libs/langchain/langchain/graphs/neo4j_graph.py

@@ -1,6 +1,7 @@
 from typing import Any, Dict, List
 
 from langchain.graphs.graph_document import GraphDocument
+from langchain.graphs.graph_store import GraphStore
 
 node_properties_query = """
 CALL apoc.meta.data()
@@ -28,7 +29,7 @@ RETURN {start: label, type: property, end: toString(other_node)} AS output
 """
 
 
-class Neo4jGraph:
+class Neo4jGraph(GraphStore):
     """Neo4j wrapper for graph operations.
 
     *Security note*: Make sure that the database connection uses credentials
@@ -80,6 +81,16 @@ class Neo4jGraph:
                 "'apoc.meta.data()' is allowed in Neo4j configuration "
             )
 
+    @property
+    def get_schema(self) -> str:
+        """Returns the schema of the Graph"""
+        return self.schema
+
+    @property
+    def get_structured_schema(self) -> Dict[str, Any]:
+        """Returns the structured schema of the Graph"""
+        return self.structured_schema
+
     def query(self, query: str, params: dict = {}) -> List[Dict[str, Any]]:
         """Query Neo4j database."""
         from neo4j.exceptions import CypherSyntaxError