Retrieving process ID from Vte.Terminal

[kiplingw]

I am using Python 3 with GObject introspection to create a Vte.Terminal widget. Up to date and reliable documentation on this widget is scarce. If one uses the fork_command_full() method to create a child process in the aforementioned terminal widget, how does one then retrieve the child process ID?

Version 0.26 of the Vte.Terminal documentation claims there is a 9th parameter to fork_command_full() method which is used to store the child's process ID, but my implementation claims there is no such parameter.

Any help appreciated.