retrofit-mock/src/main/java/retrofit2/mock/NetworkBehavior.java
@SuppressWarnings("ConstantConditions") // Guarding public API nullability.
  public static NetworkBehavior create(Random random) {
    if (random == null) throw new NullPointerException("random == null");
    return new NetworkBehavior(random);
  }
@SuppressWarnings("ConstantConditions") // Guarding public API nullability.
  public static NetworkBehavior create(Random random) {
    if (random == null) throw new NullPointerException("random == null");
    return new NetworkBehavior(random);
  }
Create an instance with default behavior which uses {@code random} to control variance and
failure calculation.