private void addChildren(ExprNodeGenericFuncDesc node) {
    for(ExprNodeDesc child: node.getChildren()) {
      parse(child);
    }
  }
Create a leaf expression when we aren't sure where the variable is
located.
@param operator the operator type that was found
@param expression the expression to check
ql/src/java/org/apache/hadoop/hive/ql/io/sarg/ConvertAstToSearchArg.java