def __init__(self, backbone, neck, head):
        """
        S2ANet, see https://arxiv.org/pdf/2008.09397.pdf

        Args:
            backbone (object): backbone instance
            neck (object): `FPN` instance
            head (object): `Head` instance
        """
        super(S2ANet, self).__init__()
        self.backbone = backbone
        self.neck = neck
        self.s2anet_head = head

        S2ANet, see https://arxiv.org/pdf/2008.09397.pdf

        Args:
            backbone (object): backbone instance
            neck (object): `FPN` instance
            head (object): `Head` instance
        
ppdet/modeling/architectures/s2anet.py