<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def uninstall_all_visa_handlers(self, session):
 """Uninstalls all previously installed handlers for a particular session. :param session: Unique logical identifier to a session. If None, operates on all sessions. """


        if session is not None:
            self.__uninstall_all_handlers_helper(session)
        else:
            for session in list(self.handlers):
                self.__uninstall_all_handlers_helper(session)