def is_bit_used_other_than_carry4_cin(design, top_module, bit, bit_to_cells):
    """ Is the net bit specified used by any sinks other than a carry chain? """
    cells = design["modules"][top_module]["cells"]
    list_of_cells = bit_to_cells[bit]
    assert len(list_of_cells) == 2, bit

    direct_cellname, port, _ = list_of_cells[1]
    direct_cell = cells[direct_cellname]
    assert direct_cell['type'] == "CARRY_CO_DIRECT"
    assert port == "CO"

    # Follow to output
    connections = direct_cell["connections"]["OUT"]
    assert len(connections) == 1

    for cellname, port, bit_idx in bit_to_cells[connections[0]][1:]:
        cell = cells[cellname]
        if cell["type"] == "CARRY_COUT_PLUG" and port == "CIN":
            continue
        else:
            return True, direct_cellname

    return False, direct_cellname