I am doing a python project about orbits using geometric integrators. I have gotten stuck on the runge-kutta 4th order method

Question

\'\'\' def RK4step(r0,v0,h):

r = math.sqrt((r0[0]**2)+(r0[1]**2))
w0 = [r0[0],r0[1],v0[0],v0[1]]
k1 = [w0[2],w0[3],((-1)*(w0[0])/r**3),((-1)*(w0[1])/r**3)]
k2