If the DistributedEvaluator is in primary mode, starts the manager
        process and returns. In this case, the ``exit_on_stop`` argument will
        be ignored.
        If the DistributedEvaluator is in secondary mode, it connects to the manager
        and waits for tasks.
        If in secondary mode and ``exit_on_stop`` is True, sys.exit() will be called
        when the connection is lost.
        ``secondary_wait`` specifies the time (in seconds) to sleep before actually
        starting when in secondary mode.
        If 'reconnect' is True, the secondary nodes will try to reconnect when
        the connection is lost. In this case, sys.exit() will only be called
        when 'exit_on_stop' is True and the primary node send a forced shutdown
        command.

def start(self, exit_on_stop=True, secondary_wait=0, reconnect=False):
        """
        If the DistributedEvaluator is in primary mode, starts the manager
        process and returns. In this case, the ``exit_on_stop`` argument will
        be ignored.
        If the DistributedEvaluator is in secondary mode, it connects to the manager
        and waits for tasks.
        If in secondary mode and ``exit_on_stop`` is True, sys.exit() will be called
        when the connection is lost.
        ``secondary_wait`` specifies the time (in seconds) to sleep before actually
        starting when in secondary mode.
        If 'reconnect' is True, the secondary nodes will try to reconnect when
        the connection is lost. In this case, sys.exit() will only be called
        when 'exit_on_stop' is True and the primary node send a forced shutdown
        command.
        """
        if self.started:
            raise RuntimeError("DistributedEvaluator already started!")
        self.started = True
        if self.mode == MODE_PRIMARY:
            self._start_primary()
        elif self.mode == MODE_SECONDARY:
            time.sleep(secondary_wait)
            self._start_secondary()
            self._secondary_loop(reconnect=reconnect)
            if exit_on_stop:
                sys.exit(0)
        else:
            raise ValueError("Invalid mode {!r}!".format(self.mode))