Function hello 

pub fn hello(dir: &Path, config: Value) -> Hello

A hello with config and one P25 system, “sys1” (index 0), with no settings of its own — set systems[0].config for those. Calls are under dir, and the plugin’s data folder is dir/data. Calls come as WAV and M4A; for a recorder without an M4A encoder, set audio_formats to ["wav"].