Base class from which CacheDescriptors derive, provides a method to fetch data for later use
Cache descriptors allow your application to specify the arguments that will be later used with another object, such as the FBFriendPickerViewController. By using a cache descriptor instance, an application can choose to fetch data ahead of the point in time where the data is needed.
Fetches and caches the data described by the cache descriptor instance, for the given session.
The to use for fetching data