How to use the atlite.aggregate.aggregate_sum function in atlite

maybe_progressbar = make_optional_progressbar(show_progress, prefix, len(yearmonths))

    for ym in maybe_progressbar(yearmonths):
        with xr.open_dataset(cutout.datasetfn(ym)) as ds:
            if 'view' in cutout.meta.attrs:
                ds = ds.sel(**cutout.meta.attrs['view'])
            da = convert_func(ds, **convert_kwds)
            results.append(aggregate_func(da, **aggregate_kwds).load())
    if 'time' in results[0].coords:
        results = xr.concat(results, dim='time')
    else:
        results = sum(results)

    if capacity_factor:
        assert aggregate_func is aggregate_sum, \
            "The arguments `matrix`, `shapes` and `layout` are incompatible with capacity_factor"
        results /= len(cutout.meta['time'])

    if per_unit or return_capacity:
        assert aggregate_func is aggregate_matrix, \
            "One of `matrix`, `shapes` and `layout` must be given for `per_unit`"
        capacity = xr.DataArray(np.asarray(matrix.sum(axis=1)).reshape(-1), [index])

    if per_unit:
        results = (results / capacity).fillna(0.)

    if return_capacity:
        return results, capacity
    else:
        return results

layout = layout.reindex_like(cutout.meta).stack(spatial=('y', 'x')).values
        else:
            assert layout.shape == cutout.shape
        matrix = (layout.reshape((1,-1))
                  if matrix is None
                  else sp.sparse.csr_matrix(matrix).dot(spdiag(layout.ravel())))

    if matrix is not None:
        matrix = sp.sparse.csr_matrix(matrix)

        if index is None:
            index = pd.RangeIndex(matrix.shape[0])
        aggregate_func = aggregate_matrix
        aggregate_kwds = dict(matrix=matrix, index=index)
    else:
        aggregate_func = aggregate_sum
        aggregate_kwds = {}

    results = []

    yearmonths = cutout.coords['year-month'].to_index()

    if isinstance(show_progress, string_types):
        prefix = show_progress
    else:
        func_name = (convert_func.__name__[len('convert_'):]
                        if convert_func.__name__.startswith('convert_')
                        else convert_func.__name__)
        prefix = 'Convert and aggregate `{}`: '.format(func_name)

    maybe_progressbar = make_optional_progressbar(show_progress, prefix, len(yearmonths))