Function pio_dist_to_format 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pio_dist_to_format(
    net: *const PioDistNetwork,
    to: *const c_char,
    warnbuf: *mut c_char,
    warnlen: usize,
    errbuf: *mut c_char,
    errlen: usize,
) -> *mut c_char

Serialize net to distribution format to (dss, pmd, or bmopf). Writing back to the format the handle was parsed from echoes the source text byte for byte; a cross-format write reports every fidelity loss in warnbuf (\n-joined). Returns the text as an owned C string (free with pio_string_free), NULL on error.