human
I wrote the below code

    @functools.wraps(fn)
    def wrapper(self, context, *args, **kwargs):
        instance = (kwargs.get('instance') or args[0])
        try:
            im = objects.InstanceMapping.get_by_instance_uuid(context, instance.uuid)
        except exception.InstanceMappingNotFound:
            LOG.error('InstanceMapping    not    found,    unable    to    target    cell', instance=instance)
            im = None
        else:
            LOG.debug('Targeting    cell    %(cell)s    for    conductor    method    %(meth)s', {'cell': im.cell_mapping.identity, 'meth': fn.__name__})
            nova_context.set_target_cell(context, im.cell_mapping)
        return fn(self, context, *args, **kwargs)
    return wrapper

What's a good function header?

Here's a good function header?
assistant
#Here's a good function header.

def targets_cell(fn):