Is it possible to register a file extension for a plugin?

[member1]

I have a scene importer plugin. I want my file type to be opened by the program(File->Open or start a program with parameters), but processed by the plugin. Is it possible?

[Puybaret]

You can't change the extensions of the files that Sweet Home 3D is able to open from a plug-in.
ContentManager.ContentType contains a USER_DEFINED option which lets a developer define some customized file extensions in a subclass of FileContentManager (like in Export to HTML5 plug-in), but this won't change the extension of the files opened by Sweet Home 3D.