code: static boolean isSymmetricOperation(Node n) {
      switch (n.getToken()) {
        case EQ: // equal
        case NE: // not equal
        case SHEQ: // exactly equal
        case SHNE: // exactly not equal
        case MUL: // multiply, unlike add it only works on numbers
          // or results NaN if any of the operators is not a number
          return true;
        default:
          break;
      }
      return false;
    }
docs: Returns true if the operator on this node is symmetric