slotsPerKESPeriod missing in Alonzo Genesis file

In the tutorials it reads we should fetch the slotsPerKESPeriod from the genesis file. This property seems to be missing in the Alonzo genesis file. What is the best practice, where should we get it from?

From here

I have the config files my question was were I can find the slotsPerKESPeriod property for Alonzo. In the Shelley genesis file it was present (“slotsPerKESPeriod”: 129600), for Alonzo it is not present in the genesis file. Why has it been removed and where can I fetch the value for Alonzo and onwards.