def __init__(self, spec: SolverSpec, stepper: Stepper):
self._ode = spec.integrator(stepper, spec.time_start, stepper.initial_value(), spec.time_bound, max_step=spec.max_timestep, \
atol=spec.absolute_tol, rtol=spec.relative_tol, vectorized=False)
self._steps = 0
self._avg_steptime = 0.0
self._tot_steptime = 0.0
self._stepper = stepper
