'Change the path used as the backing file for the persistent state.
When a new backing file is specified if a file already exists then
its contents will be added into the current state, with conflicts
between the file and memory being resolved in favor of the file
contents. The file will then be kept in sync with the (combined)
in-memory state. The syncing can be disabled by setting this to None.
:param file_path: A path on the filesystem that can be read from and
written to, or None to turn off the backing store.
:type file_path: string'

def set_backing_file(self, file_path):

    self._synchronize_backing_file()
    self._backing_file = file_path
    self._backing_file_initialized = False
    self._synchronize_backing_file()
