def METHOD_NAME(net):
    search_cell = net.stack_cell1[0].options
    keep_mask = net.stack_cell1[0].keep_mask
    num_nodes = net.stack_cell1[0].num_nodes
    nodes = []
    idx = 0
    for curr_node in range(num_nodes - 1):
        edges = []
        for prev_node in range(curr_node + 1):  # n-1 prev nodes
            for _op_name in OPS.keys():
                if keep_mask[idx]:
                    edges.append(f"{_op_name}~{prev_node}")
                idx += 1
        node_str = "|".join(edges)
        node_str = f"|{node_str}|"
        nodes.append(node_str)
    arch_str = "+".join(nodes)
    return arch_str