_fields = ()

@staticmethod

def _init():

locs = sys._getframe(1).f_locals

self = locs.pop('self')

for name, val in locs.items():

setattr(self, name, val)

def __setattr__(self, name, value):

if name.startswith('_') or name in self._fields:

super().__setattr__(name, value)

else:

raise AttributeError('No attribute %s' % name)

def __repr__(self):

return '%s(%s)' % (type(self).__name__,

', '.join(repr(getattr(self, name)) for name in self._fields))

@classmethod

def set_fields(cls):

sig = inspect.signature(cls)