Qs regarding design of YUM

Hi All,
 
I am trying to find, if there is any software design document for YUM, that lists
sequence diagrams or flows, for some yum use cases such as,
package install
package upgrade
package removal.
 
We are trying to implement a custom yum plugin hook, so that right after download of package, device will reboot. While device is powering up, during initrd phase of boot, package will get installed.
 
If there are any YUM software design document, or if there is any other easy way to determine, the flow for package install/upgrade/removal, please let me know.
 
Your help is highly appreciated.
 
Thanks,
 
SK
 
 

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