Generates a solution trajectory of variable length.

def _integrate_variable_trajectory(self, h, g, tol, step, relax):
        """Generates a solution trajectory of variable length."""
        # initialize the solution using initial condition
        solution = np.hstack((self.t, self.y))

        while self.successful():

            self.integrate(self.t + h, step, relax)
            current_step = np.hstack((self.t, self.y))
            solution = np.vstack((solution, current_step))

            if g(self.t, self.y, *self.f_params) < tol:
                break
            else:
                continue

        return solution