Pass data loader args

>>> import json
>>> from woger import Workspace, BasePathStructure, BaseData
>>>
>>> def load_json(data):
...     return json.dumps(data.passed_arg)
>>>
>>> class Data(BaseData):
...     passed_arg = lambda data: dict(value=[4, 2])
...     json = load_json
>>>
>>> data = Data()
>>> print(data.json)
{"value": [4, 2]}