Mark Vertex AI classes as serialisable (#10484)

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---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/langchain/langchain/chat_models/vertexai.py

@@ -124,6 +124,10 @@ class ChatVertexAI(_VertexAICommon, BaseChatModel):
     model_name: str = "chat-bison"
     "Underlying model name."
 
+    @classmethod
+    def is_lc_serializable(self) -> bool:
+        return True
+
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that the python package exists in environment."""

libs/langchain/langchain/llms/vertexai.py

@@ -18,7 +18,7 @@ from langchain.callbacks.manager import (
     CallbackManagerForLLMRun,
 )
 from langchain.llms.base import BaseLLM, create_base_retry_decorator
-from langchain.pydantic_v1 import BaseModel, root_validator
+from langchain.pydantic_v1 import BaseModel, Field, root_validator
 from langchain.schema import (
     Generation,
     LLMResult,
@@ -144,7 +144,7 @@ class _VertexAIBase(BaseModel):
     "Default is 5."
     max_retries: int = 6
     """The maximum number of retries to make when generating."""
-    task_executor: ClassVar[Optional[Executor]] = None
+    task_executor: ClassVar[Optional[Executor]] = Field(default=None, exclude=True)
     stop: Optional[List[str]] = None
     "Optional list of stop words to use when generating."
     model_name: Optional[str] = None
@@ -171,7 +171,7 @@ class _VertexAICommon(_VertexAIBase):
     top_k: int = 40
     "How the model selects tokens for output, the next token is selected from "
     "among the top-k most probable tokens. Top-k is ignored for Codey models."
-    credentials: Any = None
+    credentials: Any = Field(default=None, exclude=True)
     "The default custom credentials (google.auth.credentials.Credentials) to use "
     "when making API calls. If not provided, credentials will be ascertained from "
     "the environment."
@@ -229,6 +229,10 @@ class VertexAI(_VertexAICommon, BaseLLM):
     tuned_model_name: Optional[str] = None
     "The name of a tuned model. If provided, model_name is ignored."
 
+    @classmethod
+    def is_lc_serializable(self) -> bool:
+        return True
+
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that the python package exists in environment."""