parameters: (self, target)
docstring: 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
docstring_summary: Get the sub directory of directory
docstring_tokens: Get the sub directory of directory
function: 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
function_tokens: def tree ( self , target ) : raise NotImplementedError