SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function CAST (children 1)
     ExpressionList (children 2)
      Function array (children 1)
       ExpressionList (children 2)
        Literal Tuple_(\'a\', UInt64_1)
        Literal Tuple_(\'b\', UInt64_2)
      Literal \'Map(String, UInt8)\'
