def _split_chunks(l):
    """
    Generates a list of lists of neighbouring ints. `l` must not be empty.

    >>> _split_chunks([1,2,3,5,6,7,9])
    [[1,2,3],[5,6,7],[9]]

    :type l: list[int]
    :rtype list[list[int]]
    """
    ret = [[l[0]]]
    for c in l[1:]:
        if ret[-1][-1] == c - 1:
            ret[-1].append(c)
        else:
            ret.append([c])
    return ret