Speed up chain import times

libs/community/langchain_community/chains/__init__.py

@@ -4,6 +4,24 @@
 This module contains the community chains.
 """
 
-from langchain_community.chains.pebblo_retrieval.base import PebbloRetrievalQA
+import importlib
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from langchain_community.chains.pebblo_retrieval.base import PebbloRetrievalQA
 
 __all__ = ["PebbloRetrievalQA"]
+
+_module_lookup = {
+    "PebbloRetrievalQA": "langchain_community.chains.pebblo_retrieval.base"
+}
+
+
+def __getattr__(name: str) -> Any:
+    if name in _module_lookup:
+        module = importlib.import_module(_module_lookup[name])
+        return getattr(module, name)
+    raise AttributeError(f"module {__name__} has no attribute {name}")
+
+
+__all__ = list(_module_lookup.keys())