280,
        >>> # so we need to add it here
        >>> backbone.out_channels = 1280
        >>>
        >>> # let's make the network generate 5 x 3 anchors per spatial
        >>> # location, with 5 different sizes and 3 different aspect
        >>> # ratios. We have a Tuple[Tuple[int]] because each feature
        >>> # map could potentially have different sizes and
        >>> # aspect ratios
        >>> anchor_generator = AnchorGenerator(
        >>>     sizes=((8,), (16,), (32,), (64,), (128,)),
        >>>     aspect_ratios=((1.0,),)
        >>> )
        >>>
        >>> # put the pieces together inside a FCOS model
        >>> model = FCOS(
        >>>     backbone,
        >>>     num_classes=80,
        >>>     anchor_generator=anchor_generator,
        >>> )
        >>> model.eval()
        >>> x = [torch.rand(3, 300, 400), torch.rand(3, 500, 400)]
        >>> predictions = model(x)
    r'