docs: def copy(self, object_version=None, key=None):
          """Copy a tag to a given object version.
  
          :param object_version: The object version instance to copy the tag to.
              Default: current object version.
          :param key: Key of destination tag.
              Default: current tag key.
          :return: The copied object version tag.
          """
          return ObjectVersionTag.create(
              self.object_version if object_version is None else object_version,
              key or self.key,
              self.value
          )