Need multiple deserializers for same type

[Dilip Simha]

I use cereal to load and save a particular data type, let's say "class T1 { int a; int b;};"

The json file is something like:

```

{

...

...

"10" : {

  ...

  "a" : "100",

  "b" : "200",

  ....

  }

...

}

```

I use the deserializer:

cereal::JSONInputArchive *my_file = ....;

*my_file >> cereal::make_nvp(std::to_string(i), t1);

```cpp

template<class Archive>

load(Archive &ar, T1 &t1, std::uint32_t const version) 

{

....

    ar(CEREAL_NVP(a));

    ar(CEREAL_NVP(b));

....

}

```

I wish to have another deserializer that only deserializes b and skips everything else.

```cpp

template<class Archive>

load(Archive &ar, T1 &t1, std::uint32_t const version) 

{

    ar(CEREAL_NVP(b));

}

```

How do I do this ?

My real use-case type T1 has hundreds/thousands of variables and hence I can't afford to deserialize everything.