class ReLUTest(torch.autograd.Function):
@staticmethod
def forward(ctx, input):
  
    ctx.save_for_backward(input)
    input = input.clamp(min=0)

    return input

@staticmethod
def backward(ctx, grad_output):

    input, = ctx.saved_tensors
    grad_input = grad_output.clone()
    grad_input[input < 0] = 0
    return grad_input