return func_.emitWarning()
           << "Invalid number of arguments to " << kCustomSSDPostprocessing
           << ": " << func_.getNumArguments();
  }
  if (func_.getFunctionType().getNumResults() != 4) {
    return func_.emitWarning()
           << "Invalid number of results from " << kCustomSSDPostprocessing
           << ": " << func_.getFunctionType().getNumResults();
  }