'Random draw of the state disturbance vector from its conditional
distribution.
Notes
.. math::
\eta ~ N(\hat \eta, Var(\hat \eta \mid Y_n))'

@property
def simulated_state_disturbance(self):

    if (self._simulated_state_disturbance is None):
        self._simulated_state_disturbance = np.array(self._simulation_smoother.simulated_state_disturbance, copy=True)
    return self._simulated_state_disturbance
