model space "num_labels" parameter inconsistent among various classes

[btebbutt]

when using the premade model spaces e.g. mobile net , there is a parameter to change the classification layer to align with our own dataset e.g.

Why is this not a parameter for other model spaces e.g. dart space :

for the Dart model space, there is only the option to use CIFAR or IMAGENET model spaces. But what if I want to change the number of labels to 2 for my own dataset?