def _prefixscan_first(func, x, axis, dtype):
    """Compute the prefix scan (e.g., cumsum) on the first block

    Parameters
    ----------
    func : callable
        Cumulative function (e.g. ``np.cumsum``)
    x : np.array
        Current block
    axis : int
    dtype : dtype

    Returns
    -------
    np.array
    """
    return func(x, axis=axis, dtype=dtype)