langchain: support api key argument with OpenAI moderation chain (#29140)

**Description:** Makes it possible to instantiate
`OpenAIModerationChain` with an `openai_api_key` argument only and no
`OPENAI_API_KEY` environment variable defined.

**Issue:** https://github.com/langchain-ai/langchain/issues/25176

**Dependencies:** `openai`

---------

Co-authored-by: ccurme <chester.curme@gmail.com>

libs/langchain/langchain/chains/moderation.py

@@ -67,8 +67,8 @@ class OpenAIModerationChain(Chain):
             if values["openai_pre_1_0"]:
                 values["client"] = openai.Moderation
             else:
-                values["client"] = openai.OpenAI()
-                values["async_client"] = openai.AsyncOpenAI()
+                values["client"] = openai.OpenAI(api_key=openai_api_key)
+                values["async_client"] = openai.AsyncOpenAI(api_key=openai_api_key)
 
         except ImportError:
             raise ImportError(

libs/langchain/tests/integration_tests/chains/openai_functions/test_openapi.py

@@ -2,6 +2,7 @@ import json
 
 import pytest
 
+from langchain.chains import OpenAIModerationChain
 from langchain.chains.openai_functions.openapi import get_openapi_chain
 
 api_spec = {
@@ -36,3 +37,13 @@ def test_openai_openapi_chain() -> None:
     chain = get_openapi_chain(json.dumps(api_spec), llm)
     output = chain.invoke({"query": "Fetch the top two posts."})
     assert len(output["response"]) == 2
+
+
+@pytest.mark.requires("openai")
+def test_openai_moderation_chain_instantiation() -> None:
+    """Test OpenAIModerationChain."""
+    api_key = "foo"
+
+    moderation = OpenAIModerationChain(openai_api_key=api_key)
+
+    assert isinstance(moderation, OpenAIModerationChain)