json generation by components

Hi

If I have a parsys json generated does not have child components. 

whereas, if I have responsivegrid or container components then json generated has child components data as well.

Question: how does json generation works recursively.  Here is some example of content i am looking at. 

Here is some API from core components I am trying to understand https://github.com/adobe/aem-core-wcm-components/blob/a4418ab5a1b40d432432b3f904bf8c391a4940f1/bundles/core/src/main/java/com/adobe/cq/wcm/core/components/internal/models/v1/LayoutContainerImpl.java

I appreciate if someone explains the flow and API calls which actually generating below json using any specific selectors, recursion works if we have components inside components etc.

Also, if I am going to have my own custom container as such, I would like to use above API.

Thanks,

Sri