In order to use Batch with Unity, you will need to make a Unity plugin that calls the native code.

Here are Unity's documents on how to do so:

We also open-sourced our old, deprecated, Unity plugin.
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While it is not fit for production, it provides a good example of how to implement Batch in your own plugin and can work as its foundation.
​The source can be found here.

Please be aware that Batch offers no support for this plugin.