gistfile1.py

  class Entity:
    def register_fields(self, cls, fields):
      for name in fields:
        setattr(cls, name, property(lambda self: self.get_value(name))
      
    def get_value(self, name):
      return self.json[name]
 
  class Org(Entity):
    def __init__(self):
      self.register_fields(self.__class__, ["avatar_url", "billing_email"])