Gets the contents of the config files
        startup-config and private-config from NVRAM.

        :returns: tuple (startup-config, private-config) base64 encoded

def extract_config(self):
        """
        Gets the contents of the config files
        startup-config and private-config from NVRAM.

        :returns: tuple (startup-config, private-config) base64 encoded
        """

        try:
            reply = yield from self._hypervisor.send('vm extract_config "{}"'.format(self._name))
        except DynamipsError:
            # for some reason Dynamips gets frozen when it does not find the magic number in the NVRAM file.
            return None, None
        reply = reply[0].rsplit(' ', 2)[-2:]
        startup_config = reply[0][1:-1]  # get statup-config and remove single quotes
        private_config = reply[1][1:-1]  # get private-config and remove single quotes
        return startup_config, private_config