let id_string = 
  (p: string): option(string) => 
    {
      let packed: bytes = Bytes.pack(p);
      ((Bytes.unpack(packed)) : option(string))
    };

let id_int = 
  (p: int): option(int) => 
    {
      let packed: bytes = Bytes.pack(p);
      ((Bytes.unpack(packed)) : option(int))
    };

let id_address = 
  (p: address): option(address) => 
    {
      let packed: bytes = Bytes.pack(p);
      ((Bytes.unpack(packed)) : option(address))
    };