def METHOD_NAME(self):
    """Stereographic fisheye model of focal length f, defined as r/f = 2*tan(theta/2)"""
    x, y, z = self.obj_point
    r = np.linalg.norm([x, y, z])
    # Note: 2*tan(atan2(x, z)/2) = 2*x/(z+sqrt(x^2+z^2))
    self.assertAlmostEqual(2*np.tan(np.arctan2(x, z)/2), 2*x/(z+r))
    perspective_pt = self.obj_point[0:2]/self.obj_point[2]
    distorted_pt = self.stereographic.uncalibrate(perspective_pt)
    rectified_pt = self.stereographic.calibrate(distorted_pt)
    self.gtsamAssertEquals(distorted_pt, self.img_point)
    self.gtsamAssertEquals(rectified_pt, perspective_pt)