def lorentz_deriv(xxx_todo_changeme, t0, sigma=<NUM_LIT>, beta=<NUM_LIT>/<NUM_LIT:3>, rho=<NUM_LIT>):
(x, y, z) = xxx_todo_changeme<EOL>return [sigma * (y - x), x * (rho - z) - y, x * y - beta * z]<EOL>
Compute the time-derivative of a Lorentz system.