def _increment(arr, indices):
    """Increment some indices in a 1D vector of non-negative integers.
    Repeated indices are taken into account."""
    arr = _as_array(arr)
    indices = _as_array(indices)
    bbins = np.bincount(indices)
    arr[:len(bbins)] += bbins
    return arr
Increment some indices in a 1D vector of non-negative integers.
    Repeated indices are taken into account.