Ekf2 module architecture

I’m trying to understand the architecture of the estimation system, but I’m still a beginner in PX4 and cpp, I’m reading the scripts in the ekf2 module but it’s hard to figure out just where to start from, Can anyone give advice about where to start or whether it exist a “main function” that initialize the filter and perform the prediction sensor fusion and all the rest of operation by order? if so where to find it? because till know the scripts I read are just definition of classes and definition of function so I’m literally lost, thank you