code: @SuppressWarnings({ "rawtypes", "unchecked" })
      @Override
      public int compare(WritableComparable a, WritableComparable b) {
          if (a instanceof Key && b instanceof Key) {
              Comparable one = Key.class.cast(a).identifier();
              Comparable other = Key.class.cast(b).identifier();
  
              return one.compareTo(other);
          }
  
          return super.compare(a, b);
      }
docs: {@inheritDoc}