added tokens() function to Message and Chat

chatmastermind/message.py

@@ -132,6 +132,7 @@ class Question(str):
     """
     A single question with a defined header.
     """
+    tokens: int = 0   # tokens used by this question
     txt_header: ClassVar[str] = '=== QUESTION ==='
     yaml_key: ClassVar[str] = 'question'
 
@@ -165,6 +166,7 @@ class Answer(str):
     """
     A single answer with a defined header.
     """
+    tokens: int = 0  # tokens used by this answer
     txt_header: ClassVar[str] = '=== ANSWER ==='
     yaml_key: ClassVar[str] = 'answer'
 
@@ -502,3 +504,13 @@ class Message():
 
     def as_dict(self) -> dict[str, Any]:
         return asdict(self)
+
+    def tokens(self) -> int:
+        """
+        Returns the nr. of AI language tokens used by this  message.
+        If unknown, 0 is returned.
+        """
+        if self.answer:
+            return self.question.tokens + self.answer.tokens
+        else:
+            return self.question.tokens