def get_last_modified_date(
            self,
            bucket: str,
            key: str,
    ) -> datetime.datetime:
        """
        Retrieves last modified date for a given key in a given bucket.
        :param bucket: the bucket the object resides in.
        :param key: the key of the object for which the last modified date is being retrieved.
        :return: the last modified date
        """
        blob_obj = self._get_blob_obj(bucket, key)
        return blob_obj.updated