class ComplexAttribute:
    """Base descriptor class for controlled access.
    It set value to modified inner name to avoid rewriting.
    """

    _attr_template = "_attr#{}"
    inner_name: str
    outer_name: str

    def set_names(self, outer_name):
        self.inner_name = self._attr_template.format(outer_name)
        self.outer_name = outer_name

    def __get__(self, instance, owner):
        return self if instance is None else getattr(instance, self.inner_name)

    def __set__(self, instance, value):
        setattr(instance, self.inner_name, value)


class ComplexEntityMeta(type):
    """Base metaclass for classes with complex attributes.
    Set inner and outer names for attributes announced with descriptors.
    """

    def __init__(cls, name, bases, attr_dict):
        super().__init__(name, bases, attr_dict)
        for k, v in attr_dict.items():
            if isinstance(v, ComplexAttribute):
                v.set_names(k)


class ComplexEntity(metaclass=ComplexEntityMeta):
    """Base class for classes with complex attributes.
    Also present dict-like methods __contains__ and get.
    """

    def __contains__(self, item):
        return self._get_key(item) in self.__dict__

    def get(self, key, default=None):
        return self.__dict__.get(self._get_key(key), default)

    def _get_key(self, key):
        attr = self.__class__.__dict__.get(key)
        if isinstance(attr, ComplexAttribute):
            return attr.inner_name
        return key