'Returns (instance_type,image_id) for a given alias based
on the map returned from self._get_launch_map'

def _get_type_and_image_id(self, alias):

    lmap = self._get_launch_map()
    for (type, image) in lmap:
        key = (type, image)
        if (alias in lmap.get(key)):
            return key
