def get_size():
    """Return the length (in bytes) of the data this node represents. For
        directory nodes, I return the size of the backing store. I return
        synchronously and do not consult the network, so for mutable objects,
        I will return the most recently observed size for the object, or None
        if I don't remember a size. Use get_current_size, which returns a
        Deferred, if you want more up-to-date information."""
