SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function toNullable (alias k) (children 1)
     ExpressionList (children 1)
      Function toUInt256 (children 1)
       ExpressionList (children 1)
        Literal UInt64_321
   ExpressionList (children 1)
    Identifier k