code: func (a *GeneratorArgs) Rng() *rand.Rand {
  	if a.rng == nil {
  		panic("GeneratorArgs has not been initialized by NewGenerator yet")
  	}
  	return a.rng
  }
docs: // Rng returns the random number generator used by generators.
  // Panics if called before the GeneratorArgs has been initialized by NewGenerator.