Open an existing diagram

I’m working on the customization of the capella’s activity explorer. I will open an existing diagram and I know that we can righ cick in the browser and select open. The fact is that I need the code behind this open feature and I can’t find it. Besides I don’t know where I can search in the source code or what is the concerned plug-in to extract the method from the plug-in.
I hope that someone has a clue or know what I’m talking about.

I found the solution