make layer API rustic about juice HOT 5 OPEN

use co::prelude::*;

let mut discoverer = DeviceDiscoverer::new();
/// my laptop has 2 gpus 1 nvidia (CUDA and OpenCL) and integrated intel (OpenCL only) 
discoverer.add_discoverer(co::cuda::CudaDiscoverer::new()); // firstly added - higher priority 
discoverer.add_discoverer(co::opencl::OpenCLDiscoverer::only_gpu());
discoverer.add_discoverer(co::native::NativeDiscoverer::new());
let device_set = discoverer.discover(); // here we have 3 devices - [Nvidia<CUDA>, Intel<OpenCL>, CPU<Native>]
println!("Found: {}", device_set);

let backend = SharedBackend::new(device_set);

let model = build_model(backend);
let mut trainer = Trainer::new();
trainer.set_solver(Adam::new(0.01, ...));
trainer.set_model(model);
let epochs = trainer.fit_iter(1000); // run 1000 epochs
for epoc in epochs {
    println!("{}", epoch);
} 
fn build_model(b: Rc<Backend>) -> impl ILayer {
    model! {
         <Sequential input_shape=(28, 28, 1)>
              <Reshape shape=(768) />
              <Linear units={128} />
              <Activation type={Sigmoid} />
              
              <Linear units={256} />
              <Activation type={Sigmoid} />

              <Linear units={10} />
              <Activation type={Sigmoid} />
              <Softmax classes={10} />
         </Sequential>
    }
}