How to use the wradlib.io.xarray.DataArray function in wradlib

def elevation_range(self):
        """Return the elevation range of this dataset."""
        if self._elevation_range is None:
            startel = self._obj.attrs['startelA']
            stopel = self._obj.attrs['stopelA']
            elevation_data = (startel + stopel) / 2.
            da = xr.DataArray(elevation_data, dims=['dim_0'], attrs=el_attrs)
            self._elevation_range = da
        return self._elevation_range

def azimuth_range(self):
        """Return the azimuth range of this dataset."""
        if self._azimuth_range is None:
            startaz = self._obj.attrs['startazA']
            stopaz = self._obj.attrs['stopazA']
            zero_index = np.where(stopaz < startaz)
            stopaz[zero_index[0]] += 360
            azimuth_data = (startaz + stopaz) / 2.
            da = xr.DataArray(azimuth_data, attrs=az_attrs)
            self._azimuth_range = da
        return self._azimuth_range

def time_range(self):
        """Return the time range of this dataset."""
        if self._time_range is None:
            times = self._obj['timestamp'] / 1e6
            attrs = {'units': 'seconds since 1970-01-01T00:00:00Z',
                     'standard_name': 'time'}
            da = xr.DataArray(times, attrs=attrs)
            self._time_range = da
        return self._time_range

def elevation_range2(self):
        """Return the elevation range of this dataset."""
        if self._elevation_range is None:
            nrays = self._obj.attrs['nrays']
            elangle = self._obj.attrs['elangle']
            elevation_data = np.ones(nrays, dtype='float32') * elangle
            da = xr.DataArray(elevation_data, dims=['dim_0'], attrs=el_attrs)
            self._elevation_range = da
        return self._elevation_range

def prt(self):
        if self._prt is None:
            try:
                prt = 1. / self._obj.attrs['prf']
                da = xr.DataArray(prt, dims=['dim_0'])
                self._prt = da
            except KeyError:
                pass
        return self._prt

def azimuth_range2(self):
        """Return the azimuth range of this dataset."""
        if self._azimuth_range is None:
            nrays = self._obj.attrs['nrays']
            res = 360. / nrays
            azimuth_data = np.arange(res / 2.,
                                     360.,
                                     res,
                                     dtype='float32')

            da = xr.DataArray(azimuth_data, dims=['dim_0'], attrs=az_attrs)
            self._azimuth_range = da
        return self._azimuth_range