def order_by(field, desc=False):
return Filter({}).order_by(field, desc)<EOL>
Allows ordering of results.  You may only ever order a collection's results
once in a given request.  For example::

   # sort results by Instances group
   client.linode.instances(order_by(Instance.group))

:param field: The field to order results by.  Must be a filterable attribute
              of the model.
:type field: FilterableAttribute
:param desc: If True, return results in descending order.  Defaults to False
:type desc: bool

:returns: A filter that will order results as requested.
:rtype: Filter