docs: public static Object and(Object left, Object right, EvaluationContext ctx) {
          Boolean l = EvalHelper.getBooleanOrNull( left );
          Boolean r = EvalHelper.getBooleanOrNull( right );
          // have to check for all nulls first to avoid NPE
          if ( (l == null && r == null) || (l == null && r == true) || (r == null && l == true) ) {
              return null;
          } else if ( l == null || r == null ) {
              return false;
          }
          return l && r;
      }