Create own python custom client node for the mavros SetMode.srv?

edit

Hi, I want to understand the services structure of mavros.
I am following this (Sorry, I have to mention link like this, it was not displaying properly otherwise) http://library.isr.ist.utl.pt/docs/ro... to understand creation of new services, In this link, they have a "Service Client Node" script running to keep the service active.
I am searching for a similar mavros equivalent python file which create Service Client Node to keep the service running. Please tell where can i find that file?

Apparently, I am trying to create my own python custom client node which changes mode using SetMode.srv from mavros. Also, Please tell how to create own python custom client node for the mavros SetMode srv?