def METHOD_NAME(self):
    """Compute the interpolant after each step.
    Returns
    -------
    sol : rk.RkDenseOutput
        Interpolant between the last and current location.
    """
    Q = self.solver.K.T.dot(self.solver.P)
    sol = rk.RkDenseOutput(self.solver.t_old, self.solver.t, self.solver.y_old, Q)
    return sol