Composition of path structures

>>> from woger import BasePathStructure
>>>
>>> class PS1(BasePathStructure):
...     xml = 'xml'
>>>
>>> class PS2(BasePathStructure):
...     json = 'json'
>>>
>>> class PathStructure(PS1, PS2):
...     txt = 'txt'
>>>
>>> ps = PathStructure('root')
>>> print(ps.txt, ps.json, ps.xml, sep='\n')
root/txt
root/json
root/xml