MultiprocessPluginProxy is instanciated by the MultiprocessPluginManager to replace the real implementation
that is run in a different process.
You cannot access your plugin directly from the parent process. You should use the child_pipe to communicate with your plugin. The MultiprocessPluginProxy` role is to keep reference of the communication pipe to the child process as well as the process informations.
This class contains two members that are initialized by the MultiprocessPluginManager.
self.proc is a reference that holds the multiprocessing.Process instance of the child process.
self.child_pipe is a reference that holds the multiprocessing.Pipe instance to communicate with the child.