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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def decode_coords(ds, gridfile=None):
 """ Sets the coordinates and bounds in a dataset This static method sets those coordinates and bounds that are marked marked in the netCDF attributes as coordinates in :attr:`ds` (without deleting them from the variable attributes because this information is necessary for visualizing the data correctly) Parameters ds: xarray.Dataset The dataset to decode gridfile: str The path to a separate grid file or a xarray.Dataset instance which may store the coordinates used in `ds` Returns ------- xarray.Dataset `ds` with additional coordinates"""

        def add_attrs(obj):
            if 'coordinates' in obj.attrs:
                extra_coords.update(obj.attrs['coordinates'].split())
                obj.encoding['coordinates'] = obj.attrs.pop('coordinates')
            if 'bounds' in obj.attrs:
                extra_coords.add(obj.attrs['bounds'])
        if gridfile is not None and not isinstance(gridfile, xr.Dataset):
            gridfile = open_dataset(gridfile)
        extra_coords = set(ds.coords)
        for k, v in six.iteritems(ds.variables):
            add_attrs(v)
        add_attrs(ds)
        if gridfile is not None:
            ds.update({k: v for k, v in six.iteritems(gridfile.variables)
                       if k in extra_coords})
        if xr_version < (0, 11):
            ds.set_coords(extra_coords.intersection(ds.variables),
                          inplace=True)
        else:
            ds._coord_names.update(extra_coords.intersection(ds.variables))
        return ds