Class CacheAbstract

Paremeters
----------
request:
    the global request object

Overrides: object.__init__

Tries retrieve the value corresponding to `key` from the cache of the
object exists and if it did not expire, else it called the function `f`
and stores the output in the cache corresponding to `key`. In the case
the output of the function is returned.

:param key: the key of the object to be store or retrieved
:param f: the function, whose output is to be cached
:param time_expire: expiration of the cache in microseconds

- `time_expire` is used to compare the current time with the time when
    the requested object was last saved in cache. It does not affect
    future requests.
- Setting `time_expire` to 0 or negative value forces the cache to
    refresh.

If the function `f` is `None` the cache is cleared.

Clears the cache of all keys that match the provided regular expression.
If no regular expression is provided, it clears all entries in cache.

Parameters
----------
regex:
    if provided, only keys matching the regex will be cleared.
    Otherwise all keys are cleared.

Increments the cached value for the given key by the amount in value

Parameters
----------
key:
    key for the cached object to be incremeneted
value:
    amount of the increment (defaults to 1, can be negative)