Function pio_from_json 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pio_from_json(
    json: *const c_char,
    errbuf: *mut c_char,
    errlen: usize,
) -> *mut PioNetwork

Rebuild a network handle from JSON produced by pio_to_json. Returns a new handle (free with pio_network_free), or NULL on error (message into errbuf). The handle has no retained source, so pio_to_matpower reformats it rather than echoing a byte-exact original.