[NEST Users] About the Izhikevich model

Dear NEST Community, When I use NEST, I find that Izhikevich model has no refractory period. Whether there is a specific reason for this setting or whether the model itself does not have this refractory period? After all, according to my understanding, all neurons in biology have the characteristics of refractory period. I would be happy to get any feedback on it. Thanks, Chao.