def all(self, category=None, return_key_and_category=False):
        """
        Get all tags in this handler.

        Args:
            category (str, optional): The Tag category to limit the
                request to. Note that `None` is the valid, default
                category.
            return_key_and_category (bool, optional): Return a list of
                tuples `[(key, category), ...]`.

        Returns:
            tags (list): A list of tag keys `[tagkey, tagkey, ...]` or
                a list of tuples `[(key, category), ...]` if
                `return_key_and_category` is set.

        """
        if self._cache not in None or not _TYPECLASS_AGGRESSIVE_CACHE:
            self._recache()
        if category:
            category = category.strip().lower() if category is not None else None
            matches = [tag for tag in self._cache.values() if tag.db_category == category]
        else:
            matches = self._cache.values()

        if matches:
            matches = sorted(matches, key=lambda o: o.id)
            if return_key_and_category:
                # return tuple (key, category)
                return [(to_str(p.db_key), to_str(p.db_category)) for p in matches]
            else:
                return [to_str(p.db_key) for p in matches]
        return []
dataset/ETHPy150Open evennia/evennia/evennia/typeclasses/tags.py/TagHandler.all/operator `is` -> `not in`