SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function sumMap (children 1)
     ExpressionList (children 2)
      Literal Array_[\'a\', \'b\']
      Function array (children 1)
       ExpressionList (children 2)
        Literal UInt64_1
        Function toNullable (children 1)
         ExpressionList (children 1)
          Literal UInt64_0