Hi,
It is similar to nn.Module in PyTorch. You can combine your classes however you want to creating a class that derives nn.Module. Here is example:
class Combined(nn.Module):
    def __init__(self, model1, model2):
        super(Combined, self).__init__()
        self.first_model=model1
        self.second_model=model2

    def forward(self, inputs):
        outputs1 = self.first_model(inputs)
        outputs2 = self.second_model(inputs)
        # or anything you want can be done here
        return outputs1, outputs2

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