def _find_new_name(old_name, node_names):
    """Disambiguate a node's name from a list of existing node names by adding
    successively larger integers.
    """
    count = 0
    new_name = old_name + "." + str(count)
    while new_name in node_names:
        count += 1
        new_name = old_name + "." + str(count)
    return new_name