private boolean append(Object k, Object v, boolean sep) throws IOException {
if (k == null) throw new IllegalArgumentException(ERR_NULL_KEY);
if (v == null) return false;
String key = k.toString();
if (jay.include(key)) {
if (sep) w.write(',');
w.write('"');
w.write(jay.mapToJson(key));
w.write('"');
w.write(':');
appendValue(v);
return true;
}
return false;
}
