(self, target)
Get the sub directory of directory

        :param target: The hash of the target directory.
        :return: list - a list of containing the names of sub directories
Get the sub directory of directory
Get the sub directory of directory
def tree(self, target):
        """ Get the sub directory of directory

        :param target: The hash of the target directory.
        :return: list - a list of containing the names of sub directories
        """
        raise NotImplementedError
def tree ( self , target ) : raise NotImplementedError