Tells if the data is already defined

Retrieves the value from the storage bucket; returns a Storage_error if the key is not set or if the deserialisation fails

Retrieves the value from the storage bucket ; returns None if the data is not initialized, or Storage_helpers.Storage_error if the deserialisation fails

Allocates the storage bucket and initializes it ; returns a Storage_errorExisting_key if the bucket exists

Updates the content of the bucket; returns a Storage_Error Missing_key if the value does not exist

Allocates the data and initializes it with a value ; just updates it if the bucket exists

When the value is Some v, allocates the data and initializes it with v ; just updates it if the bucket exists. When the value is None, deletes the storage bucket; it does nothing if the bucket does not exists.

Delete the storage bucket ; returns a Storage_error Missing_key if the bucket does not exists

Removes the storage bucket and its contents; does nothing if the bucket does not exist