code: def _validate_tag_key(self, tag_key, exception_param='tags.X.member.key'):
          
          # Validate that the key length is correct:
          if len(tag_key) > 128:
              raise TagKeyTooBig(tag_key, param=exception_param)
  
          # Validate that the tag key fits the proper Regex:
          # [\w\s_.:/=+\-@]+ SHOULD be the same as the Java regex on the AWS documentation: [\p{L}\p{Z}\p{N}_.:/=+\-@]+
          match = re.findall(r'[\w\s_.:/=+\-@]+', tag_key)
          # Kudos if you can come up with a better way of doing a global search :)
          if not len(match) or len(match[0]) < len(tag_key):
              raise InvalidTagCharacters(tag_key, param=exception_param)
docs: Validates the tag key.
  
          :param all_tags: Dict to check if there is a duplicate tag.
          :param tag_key: The tag key to check against.
          :param exception_param: The exception parameter to send over to help format the message. This is to reflect
                                  the difference between the tag and untag APIs.
          :return: