code: public BeanComparator nullLow() {
          BeanComparator bc = new BeanComparator(this);
          bc.mOrderByName = mOrderByName;
          bc.mUsingComparator = mUsingComparator;
          bc.mFlags = mFlags ^ ((~mFlags & 0x01) << 1);
          return bc;
      }
docs: Set the order of comparisons against null as being low
  on just the last {@link #orderBy order-by} property. If no order-by
  properties have been specified, then null low order is applied to the
  compared beans.
  <p>
  Calling 'reverse, nullLow' is equivalent to calling 'nullHigh, reverse'.