(*
       (define (Y f) ((lambda (x) (f (x x)))
                      (lambda (x) (f (x x)))))
     *)
    Definition Y : sexp :=
      node [atom "define"; node [atom "Y"; atom "f"];
              node [node [atom "lambda"; node [atom "x"]; node [atom "f"; node [atom "x"; atom "x"]]];
                      node [atom "lambda"; node [atom "x"]; node [atom "f"; node [atom "x"; atom "x"]]]]]
           %string.

Lemma foo' : ByteListReader.unwrap deserialize (IOStreamWriter.unwrap (serialize Y)) = Some (Y, []).