<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def resume(self):
 """ Resumes execution on all threads of the process. @raise WindowsError: On error an exception is raised. """

        if self.get_thread_count() == 0:
            self.scan_threads() # only refresh the snapshot if empty
        resumed = list()
        try:
            for aThread in self.iter_threads():
                aThread.resume()
                resumed.append(aThread)
        except Exception:
            for aThread in resumed:
                try:
                    aThread.suspend()
                except Exception:
                    pass
            raise