'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):

    deps = []
    if self.need_top_grad():
        deps.extend(out_grad)
    deps.extend(in_data)
    deps.extend(out_data)
    return deps
