message: added rename_tags() function and test

chatmastermind/message.py

@@ -5,7 +5,7 @@ import pathlib
 import yaml
 from typing import Type, TypeVar, ClassVar, Optional, Any, Union, Final, Literal, Iterable
 from dataclasses import dataclass, asdict, field
-from .tags import Tag, TagLine, TagError, match_tags
+from .tags import Tag, TagLine, TagError, match_tags, rename_tags
 
 QuestionInst = TypeVar('QuestionInst', bound='Question')
 AnswerInst = TypeVar('AnswerInst', bound='Answer')
@@ -499,6 +499,14 @@ class Message():
             return False
         return True
 
+    def rename_tags(self, tags_rename: set[tuple[Tag, Tag]]) -> None:
+        """
+        Renames the given tags. The first tuple element is the old name,
+        the second one is the new name.
+        """
+        if self.tags:
+            self.tags = rename_tags(self.tags, tags_rename)
+
     def msg_id(self) -> str:
         """
         Returns an ID that is unique throughout all messages in the same (DB) directory.