Error 30 when updating keyfile
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It is a nested dictionary whose contents maps cache aliases to a dictionary containing the options for an individual cache.
The cache; any number of additional caches may also be specified.
If you are using a cache backend other than the local memory cache, or you need to define multiple caches, other options will be required. A string containing a dotted path to a function (or any callable) that defines how to compose a prefix, version and key into a final cache key.
The default implementation is equivalent to the function: (Empty string) The location of the cache to use.
This might be the directory for a file system cache, a host and port for a memcache server, or simply an identifying name for a local memory cache.