Ability to add MessageTransforms to the GroupChat's Select Speaker nested chat (speaker_selection_method='auto') (#2719)

* Initial commit with ability to add transforms to GroupChat

* Added tests

* Tidy up

* Tidy up of variable names and commented out test

* Tidy up comment

* Update import to relative

* Added documentation topic for transform messages for speaker selection.

* Added handling of non-core module, transforms, in groupchat

* Adjusted parameter if module not loaded.

* Updated groupchat test which failed during CI/CD

---------

Co-authored-by: Li Jiang <bnujli@gmail.com>

test/agentchat/test_groupchat.py

@@ -12,6 +12,7 @@ from test_assistant_agent import KEY_LOC, OAI_CONFIG_LIST
 
 import autogen
 from autogen import Agent, AssistantAgent, GroupChat, GroupChatManager
+from autogen.agentchat.contrib.capabilities import transform_messages, transforms
 from autogen.exception_utils import AgentNameConflict, UndefinedNextAgent
 
 
@@ -2061,6 +2062,46 @@ def test_manager_resume_messages():
         return_agent, return_message = manager.resume(messages="Let's get this conversation started.")
 
 
+def test_select_speaker_transform_messages():
+    """Tests adding transform messages to a GroupChat for speaker selection when in 'auto' mode"""
+
+    # Test adding a TransformMessages to a group chat
+    test_add_transforms = transform_messages.TransformMessages(
+        transforms=[
+            transforms.MessageHistoryLimiter(max_messages=10),
+            transforms.MessageTokenLimiter(max_tokens=3000, max_tokens_per_message=500, min_tokens=300),
+        ]
+    )
+
+    coder = AssistantAgent(name="Coder", llm_config=None)
+    groupchat = GroupChat(messages=[], agents=[coder], select_speaker_transform_messages=test_add_transforms)
+
+    # Ensure the transform have been added to the GroupChat
+    assert groupchat._speaker_selection_transforms == test_add_transforms
+
+    # Attempt to add a non MessageTransforms object, such as a list of transforms
+    with pytest.raises(ValueError, match="select_speaker_transform_messages must be None or MessageTransforms."):
+        groupchat = GroupChat(
+            messages=[],
+            agents=[coder],
+            select_speaker_transform_messages=[transforms.MessageHistoryLimiter(max_messages=10)],
+        )
+
+    # Ensure if we don't pass any transforms in, none are on the GroupChat
+    groupchat_missing = GroupChat(messages=[], agents=[coder])
+
+    assert groupchat_missing._speaker_selection_transforms is None
+
+    # Ensure we can pass in None
+    groupchat_none = GroupChat(
+        messages=[],
+        agents=[coder],
+        select_speaker_transform_messages=None,
+    )
+
+    assert groupchat_none._speaker_selection_transforms is None
+
+
 if __name__ == "__main__":
     # test_func_call_groupchat()
     # test_broadcast()
@@ -2089,4 +2130,5 @@ if __name__ == "__main__":
     test_manager_resume_functions()
     # test_manager_resume_returns()
     # test_manager_resume_messages()
+    # test_select_speaker_transform_messages()
     pass