on
Invoked each time a path is returned by delegate. This returns the path to return to the caller, which should be path itself or a path on this that corresponds to it.
Subclasses may override this to log accesses, fail on unexpected path accesses, or map directories or path names.
The base implementation returns path.
Return
the path to return to the caller.
Parameters
path
the path returned by any of the functions of this.
function
a string like "canonicalize" or "list".