code: @NonNull
    public RequestCreator placeholder(@DrawableRes int placeholderResId) {
      if (!setPlaceholder) {
        throw new IllegalStateException("Already explicitly declared as no placeholder.");
      }
      if (placeholderResId == 0) {
        throw new IllegalArgumentException("Placeholder image resource invalid.");
      }
      if (placeholderDrawable != null) {
        throw new IllegalStateException("Placeholder image already set.");
      }
      this.placeholderResId = placeholderResId;
      return this;
    }
docs: A placeholder drawable to be used while the image is being loaded. If the requested image is
  not immediately available in the memory cache then this resource will be set on the target
  {@link ImageView}.