SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function overlay (children 1)
     ExpressionList (children 5)
      Literal \'hello\'
      Literal \'world\'
      Literal UInt64_2
      Literal UInt64_3
      Literal \'extra\'