docs: def Start(self):
      """Calls the Update() method of a given VFSFile/VFSDirectory object."""
      self.Init()
      fd = aff4.FACTORY.Open(self.args.vfs_file_urn, mode="rw", token=self.token)
  
      # Account for implicit directories.
      if fd.Get(fd.Schema.TYPE) is None:
        fd = fd.Upgrade(standard.VFSDirectory)
  
      self.state.get_file_flow_urn = fd.Update(attribute=self.args.attribute)