Add max nodes limit for graph retrieval of networkX

• Set MAX_GRAPH_NODES env var (default 1000)
• Change edge type to "RELATED"

lightrag/api/routers/graph_routes.py

@@ -16,12 +16,27 @@ def create_graph_routes(rag, api_key: Optional[str] = None):
 
     @router.get("/graph/label/list", dependencies=[Depends(optional_api_key)])
     async def get_graph_labels():
-        """Get all graph labels"""
+        """
+        Get all graph labels
+
+        Returns:
+            List[str]: List of graph labels
+        """
         return await rag.get_graph_labels()
 
     @router.get("/graphs", dependencies=[Depends(optional_api_key)])
     async def get_knowledge_graph(label: str, max_depth: int = 3):
-        """Get knowledge graph for a specific label"""
+        """
+        Get knowledge graph for a specific label.
+        Maximum number of nodes is limited to env MAX_GRAPH_NODES(default: 1000)
+
+        Args:
+            label (str): Label to get knowledge graph for
+            max_depth (int, optional): Maximum depth of graph. Defaults to 3.
+
+        Returns:
+            Dict[str, List[str]]: Knowledge graph for label
+        """
         return await rag.get_knowledge_graph(node_label=label, max_depth=max_depth)
 
     return router