Declare dependencies of this operator for backward pass.

        Parameters
        ----------
        out_grad : list of int
            ids of out_grad blobs.
        in_data : list of int
            ids of in_data blobs.
        out_data: list of int
            ids of out_data blobs.

        Returns
        -------
        deps : list of int
            ids of the needed blobs.

def declare_backward_dependency(self, out_grad, in_data, out_data):
        """Declare dependencies of this operator for backward pass.

        Parameters
        ----------
        out_grad : list of int
            ids of out_grad blobs.
        in_data : list of int
            ids of in_data blobs.
        out_data: list of int
            ids of out_data blobs.

        Returns
        -------
        deps : list of int
            ids of the needed blobs.
        """
        deps = []
        if self.need_top_grad():
            deps.extend(out_grad)
        deps.extend(in_data)
        deps.extend(out_data)
        return deps