fix: resolve Pydantic test failure and CI linting error

Author: RN

libs/community/langchain_community/chat_models/mlx.py

@@ -73,9 +73,7 @@ def _parse_react_tool_calls(
     invalid_tool_calls: list[InvalidToolCall] = []
 
     bracket_pattern = r"Action:\s*(?P<name>[\w.-]+)\[(?P<input>[^\]]+)\]"
-    separate_pattern = (
-        r"Action:\s*(?P<name>[^\n]+)\nAction Input:\s*(?P<input>[^\n]+)"
-    )
+    separate_pattern = r"Action:\s*(?P<name>[^\n]+)\nAction Input:\s*(?P<input>[^\n]+)"
 
     matches = list(re.finditer(bracket_pattern, text))
     if not matches:

libs/community/tests/unit_tests/chat_models/test_mlx.py

@@ -1,11 +1,13 @@
 """Test MLX Chat wrapper."""
 
 from importlib import import_module
+from typing import Any
 
 import pytest
 from langchain_core.messages import HumanMessage
 
 from langchain_community.chat_models.mlx import ChatMLX
+from langchain_community.llms.mlx_pipeline import MLXPipeline
 
 
 class _FakeTokenizer:
@@ -24,7 +26,12 @@ def apply_chat_template(
         return "prompt"
 
 
-class _FakeLLM:
+class _FakeLLM(MLXPipeline):
+    model_id: str = "fake-model"
+    model: Any = None
+    tokenizer: Any = None
+    pipeline_kwargs: dict = {}
+
     def __init__(self) -> None:
         self.tokenizer = _FakeTokenizer()