@abstractmethod
def walk(self, top):
    'Generate the file names in a directory tree by walking the tree.\n        Input:\n        - top: starting point for walk (str)\n        Return:\n        - tuples of (root, dirs, files) \n        '
    pass
Generate the file names in a directory tree by walking the tree.
Input:
- top: starting point for walk (str)
Return:
- tuples of (root, dirs, files)
@abstractmethod
def walk(self, top):
    'Generate the file names in a directory tree by walking the tree.\n        Input:\n        - top: starting point for walk (str)\n        Return:\n        - tuples of (root, dirs, files) \n        '
    pass