code: public Object[] acceptOperands(QueryNodeVisitor visitor, Object data) throws RepositoryException {
          if (operands == null) {
              return EMPTY;
          }
  
          List<Object> result = new ArrayList<Object>(operands.size());
          for (int i = 0; i < operands.size(); i++) {
             Object r = operands.get(i).accept(visitor, data);
              if (r != null) {
                  result.add(r);
              }
          }
          return (Object[])result.toArray();
      }
docs: Helper class to accept a <code>visitor</code> for all operands
  of this <code>NAryQueryNode</code>.
  
  @param visitor the visitor to call back.
  @param data    arbitrary data for the visitor.
  @return the return values of the <code>visitor.visit()</code> calls.
  @throws RepositoryException