def METHOD_NAME(self, from_path, to_path):
    if from_path == to_path:
        return
    self.refs[from_path].add(to_path)
    self.deps[to_path].add(from_path)
    if from_path in self.white:  # no longer without references
        self.white.remove(from_path)
        self.grey.add(from_path)