SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function CAST (alias m) (children 1)
     ExpressionList (children 2)
      Function map (children 1)
       ExpressionList (children 4)
        Literal \'foo\'
        Literal Tuple_(UInt64_1, UInt64_2)
        Literal \'bar\'
        Literal Tuple_(UInt64_3, UInt64_4)
      Literal \'Map(String, Tuple(a UInt64, b UInt64))\'
   ExpressionList (children 4)
    Identifier m.keys
    Identifier m.values
    Identifier m.values.a
    Identifier m.values.b
