How to use the wradlib.georef.projection.get_default_projection function in wradlib

lon0 = 10.  # central meridian of projection
            lat0 = 60.  # standard parallel of projection

            sinlat0 = np.sin(np.radians(lat0))

            fac = (6370.040 ** 2.) * ((1. + sinlat0) ** 2.)
            lon = np.degrees(np.arctan((-x / y))) + lon0
            lat = np.degrees(np.arcsin((fac - (x ** 2. + y ** 2.)) /
                                       (fac + (x ** 2. + y ** 2.))))
            radolan_grid = np.dstack((lon, lat))
        else:
            # create radolan projection osr object
            proj_stereo = projection.create_osr("dwd-radolan")

            # create wgs84 projection osr object
            proj_wgs = projection.get_default_projection()

            radolan_grid = projection.reproject(radolan_grid,
                                                projection_source=proj_stereo,
                                                projection_target=proj_wgs)

    return radolan_grid

# as described in the format description
        phi_0 = np.radians(60)
        phi_m = np.radians(lat)
        lam_0 = 10
        lam_m = lon
        lam = np.radians(lam_m - lam_0)
        er = 6370.040
        m_phi = (1 + np.sin(phi_0)) / (1 + np.sin(phi_m))
        x = er * m_phi * np.cos(phi_m) * np.sin(lam)
        y = - er * m_phi * np.cos(phi_m) * np.cos(lam)
    else:
        # create radolan projection osr object
        proj_stereo = projection.create_osr("dwd-radolan")

        # create wgs84 projection osr object
        proj_wgs = projection.get_default_projection()

        x, y = projection.reproject(lon, lat, projection_source=proj_wgs,
                                    projection_target=proj_stereo)

    return x, y

9.0000, 48.0000,  0.0000
     9.0000, 48.0000,  0.0000
     9.0000, 48.9981, 725.7160
    10.4872, 47.9904, 725.7160
     9.0000, 47.0017, 725.7160
     7.5131, 47.9904, 1694.2234

    Here, the coordinates of the east and west directions won't come to lie on
    the latitude of the site because the beam doesn't travel along the latitude
    circle but along a great circle.

    See :ref:`/notebooks/basics/wradlib_workflow.ipynb#\
Georeferencing-and-Projection`.
    """
    if proj is None:
        proj = projection.get_default_projection()

    xyz, rad = spherical_to_xyz(r, phi, theta, sitecoords, re=re, ke=ke,
                                squeeze=True)

    # reproject aeqd to destination projection
    coords = projection.reproject(xyz, projection_source=rad,
                                  projection_target=proj)

    return coords