Update chat_messages.py

[leeivan1007]

I try a toy same by using run.py

python run.py --task "A bird is flying" --name "A bird"

And it shows:

ChatMessage(role_name=self.role_name, role_type=self.role_type, 
TypeError: __init__() got an unexpected keyword argument 'annotations'

I add an attribute (annotations) to class ChatMessage. And It is solved.