def compute_ci_red_edge(dataset):
    """Compute CI_Red_Edge vegetation index.

    Parameters
    ----------
    dataset : xarray dataset

    Returns
    -------
    xarray dataset
        Adds 'ci_red_edge' xr array to xr dataset.

    """
    b5 = dataset.band_data.sel(band="B5")
    b7 = dataset.band_data.sel(band="B7")
    ci_red_edge = (b7 / b5) - 1
    return dataset.assign({"ci_red_edge": ci_red_edge})