code: private boolean is_locked(Key<Job> job_key) { 
      if( _lockers==null ) return false;
      for( int i=(_lockers.length==1?0:1); i<_lockers.length; i++ ) {
        Key k = _lockers[i];
        if( job_key==k || (job_key != null && k != null && job_key.equals(k)) ) return true;
      }
      return false;
    }
docs: Accessors for locking state.  Minimal self-checking; primitive results