Make ChatAgent an ABC (#5129)

python/packages/autogen-agentchat/src/autogen_agentchat/base/_chat_agent.py

@@ -1,5 +1,6 @@
+from abc import ABC, abstractmethod
 from dataclasses import dataclass
-from typing import Any, AsyncGenerator, Mapping, Protocol, Sequence, runtime_checkable
+from typing import Any, AsyncGenerator, Mapping, Sequence
 
 from autogen_core import CancellationToken
 
@@ -19,17 +20,18 @@ class Response:
     or :class:`ChatMessage`."""
 
 
-@runtime_checkable
+class ChatAgent(ABC, TaskRunner):
-class ChatAgent(TaskRunner, Protocol):
     """Protocol for a chat agent."""
 
     @property
+    @abstractmethod
     def name(self) -> str:
         """The name of the agent. This is used by team to uniquely identify
         the agent. It should be unique within the team."""
         ...
 
     @property
+    @abstractmethod
     def description(self) -> str:
         """The description of the agent. This is used by team to
         make decisions about which agents to use. The description should
@@ -37,15 +39,18 @@ class ChatAgent(TaskRunner, Protocol):
         ...
 
     @property
+    @abstractmethod
     def produced_message_types(self) -> Sequence[type[ChatMessage]]:
         """The types of messages that the agent produces in the
         :attr:`Response.chat_message` field. They must be :class:`ChatMessage` types."""
         ...
 
+    @abstractmethod
     async def on_messages(self, messages: Sequence[ChatMessage], cancellation_token: CancellationToken) -> Response:
         """Handles incoming messages and returns a response."""
         ...
 
+    @abstractmethod
     def on_messages_stream(
         self, messages: Sequence[ChatMessage], cancellation_token: CancellationToken
     ) -> AsyncGenerator[AgentEvent | ChatMessage | Response, None]:
@@ -53,18 +58,22 @@ class ChatAgent(TaskRunner, Protocol):
         and the final item is the response."""
         ...
 
+    @abstractmethod
     async def on_reset(self, cancellation_token: CancellationToken) -> None:
         """Resets the agent to its initialization state."""
         ...
 
+    @abstractmethod
     async def save_state(self) -> Mapping[str, Any]:
         """Save agent state for later restoration"""
         ...
 
+    @abstractmethod
     async def load_state(self, state: Mapping[str, Any]) -> None:
         """Restore agent from saved state"""
         ...
 
+    @abstractmethod
     async def close(self) -> None:
         """Called when the runtime is stopped or any stop method is called"""
         ...