Your code is still not executable, which makes debugging hard.
After removing the undefined normalize calls and trying to setup random inputs based on the shape error messages, this code works partly:
a = torch.randn(1, 1, 2, 224, 224)
b = a.clone()
c = a.clone()
out_1 = model_1(a)
out_2 = model_2(b)
out_3 = model_3(out_1+out_2)

However, out_1 as well as out_2 are list objects, to summing them won’t work.
If I try to sum out_1[0] with out_2[0], the shape doesn’t match the expected input channels.
Could you the necessary shapes to execute the code, please?