code: @Override
      public boolean matches(IAtom atom) {
          // XXX: this is incorrect but bug 824 expects this behaviour. The reason
          //      Daylight matches is because the explicit hydrogens are
          //      suppressed by default turning on explicit hydrogens in depict
          //      match shows correct functionality. Discussion needed to revert
          //      but because other invariants aren't adjusted (implicit h) we
          //      can't really do this and the correct option is to enable/disable
          //      hydrogen suppression (removal of explicit H atoms) as a prepossessing
          //      step
          return invariants(atom).connectivity() - invariants(atom).totalHydrogenCount() == degree;
      }
docs: {@inheritDoc}