If you want to only have two class, positive vs. negative, you can:


First label the data, if you don’t already have. Then add one or two layers at the end of the network you pre-trained, freeze the pre-trained network, and only the last few layers on the new data.


The simplest is just to write a function, to pick out the pos and neg labels. For instance, the {ants, bees} could be one-hot encoded as {0001, 0100}, and write a “filter function” such as


if <pred_label> in [0001, 0100, ...]:
    <pred_label> = True // positive
else:
    <pred_label> = False // negative