<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def apply_enhancement(data, func, exclude=None, separate=False, pass_dask=False):
 """Apply `func` to the provided data. Args: data (xarray.DataArray):
 Data to be modified inplace. func (callable):
 Function to be applied to an xarray exclude (iterable):
 Bands in the 'bands' dimension to not include in the calculations. separate (bool):
 Apply `func` one band at a time. Default is False. pass_dask (bool):
 Pass the underlying dask array instead of the xarray.DataArray. """

    attrs = data.attrs
    bands = data.coords['bands'].values
    if exclude is None:
        exclude = ['A'] if 'A' in bands else []

    if separate:
        data_arrs = []
        for idx, band_name in enumerate(bands):
            band_data = data.sel(bands=[band_name])
            if band_name in exclude:
                # don't modify alpha
                data_arrs.append(band_data)
                continue

            if pass_dask:
                dims = band_data.dims
                coords = band_data.coords
                d_arr = func(band_data.data, index=idx)
                band_data = xr.DataArray(d_arr, dims=dims, coords=coords)
            else:
                band_data = func(band_data, index=idx)
            data_arrs.append(band_data)
            # we assume that the func can add attrs
            attrs.update(band_data.attrs)

        data.data = xr.concat(data_arrs, dim='bands').data
        data.attrs = attrs
        return data
    else:
        band_data = data.sel(bands=[b for b in bands
                                    if b not in exclude])
        if pass_dask:
            dims = band_data.dims
            coords = band_data.coords
            d_arr = func(band_data.data)
            band_data = xr.DataArray(d_arr, dims=dims, coords=coords)
        else:
            band_data = func(band_data)

        attrs.update(band_data.attrs)
        # combine the new data with the excluded data
        new_data = xr.concat([band_data, data.sel(bands=exclude)],
                             dim='bands')
        data.data = new_data.sel(bands=bands).data
        data.attrs = attrs

    return data