SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function map (alias m) (children 1)
     ExpressionList (children 4)
      Literal \'foo\'
      Literal UInt64_1
      Literal \'bar\'
      Literal UInt64_2
   ExpressionList (children 2)
    Identifier m.keys
    Identifier m.values
