Function pio_scopf_to_json 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pio_scopf_to_json(
    instance: *const PioScopfInstance,
    errbuf: *mut c_char,
    errlen: usize,
) -> *mut c_char

Serialize a SCOPF instance as its Julia compatibility document. The JSON records its schema version and index base. Free the returned string with pio_string_free. Returns NULL for a null handle or serialization error.