def get_index(idx_list1, idx_list2, idx_list3):
    """Function to get index list

    Function 'get_index' returns the common value between the 3 different lists

    Args:
        idx_list1 (list): list of indexes (integer)
        idx_list2 (list): list of indexes (integer)
        idx_list3 (list): list of indexes (integer)

    Returns:
        find_idx (list): list of index (integer) common in the 3 lists
    """

    # List of index of elements which have the same index in vectors list, list1, list2
    find_idx = []

    # Fill   the liste find_index
    for idx1 in idx_list1:
        for idx2 in idx_list2:
            for idx3 in idx_list3:
                if idx1 == idx2 == idx3:
                    find_idx.append(idx1)

    return find_idx