docs: def Release(self):
      """Remove the lock.
  
      Note that this only resets the lock if we actually hold it since
      lock_expiration == self.expires and lock_owner = self.lock_token.
      """
      if self.locked:
        query = ("UPDATE locks SET lock_expiration=0, lock_owner=0 "
                 "WHERE lock_expiration=%s "
                 "AND lock_owner=%s "
                 "AND subject_hash=unhex(md5(%s))")
        args = [self.expires, self.lock_token, self.subject]
        self.store.ExecuteQuery(query, args)
        self.locked = False