docs: public void findUnsafeOperatorsForDDL(UnsafeOperatorsForDDL ops) {
          if ( ! m_type.isSafeForDDL()) {
              ops.add(m_type.symbol());
          }
          if (m_left != null) {
              m_left.findUnsafeOperatorsForDDL(ops);
          }
          if (m_right != null) {
              m_right.findUnsafeOperatorsForDDL(ops);
          }
          if (m_args != null) {
              for (AbstractExpression arg : m_args) {
                  arg.findUnsafeOperatorsForDDL(ops);
              }
          }
      }