'Use hotplug to add a network interface to a running instance.
The counter action to this is :func:`detach_interface`.
:param context: The request context.
:param nova.objects.instance.Instance instance:
The instance which will get an additional network interface.
:param nova.objects.ImageMeta image_meta:
The metadata of the image of the instance.
:param nova.network.model.VIF vif:
The object which has the information about the interface to attach.
:raise nova.exception.NovaException: If the attach fails.
:returns: None'

def attach_interface(self, context, instance, image_meta, vif):

    self.plug_vifs(instance, [vif])
