def METHOD_NAME(self, x_guest, x_host):
    if self.need_guest:
        g_out = self.guest_model(x_guest)
    else:
        g_out = 0
    h_out = None
    if isinstance(x_host, list):
        for m, data in zip(self.host_model, x_host):
            out_ = m(data)
            if h_out is None:
                h_out = out_
            else:
                h_out += out_
    else:
        h_out = self.host_model[0](x_host)
    return self.activation(g_out + h_out)