'Returns the database _id and son structured lookup to find the given asset location.'

@classmethod
def asset_db_key(cls, location):

    dbkey = SON(((field_name, getattr(location, field_name)) for field_name in cls.ordered_key_fields))
    if getattr(location, 'deprecated', False):
        content_id = dbkey
    else:
        dbkey['run'] = location.run
        content_id = unicode(location.for_branch(None))
    return (content_id, dbkey)
