num_classes during model creation

[Martí Mas Fullana]

If my understanding is correct, when you do:

self.class_embed = nn.Linear(hidden_dim, num_classes)

at DeformableDETR() in deformable_detr.py, "num_classes" should instead be "num_classes + 1"

The same thing goes for:

self.class_embed.bias.data = torch.ones(num_classes) * bias_value

in the same DeformableDETR() function, where it should be "num_classes + 1" instead of "num_classes".

Otherwise I'm just getting confused somewhere, but I'm pretty sure there should be an extra background class logit.

That is how it was done in the original DETR code anyways.