getInt method
Implementation
int getInt(String key, [int defaultValue = -1]) {
  final ckey = key.toNativeUtf8().cast<ffi.Char>();
  final crval = calloc<ffi.Int>();
  cfeatures2d.cv_flann_IndexParams_getInt(ref, ckey, defaultValue, crval);
  calloc.free(ckey);
  final rval = crval.value;
  calloc.free(crval);
  return rval;
}