from typing import *
from typing import GenericMeta  # needed for python3 runtime
import six

class _DestroyableMeta(type): pass

class Destroyable(six.with_metaclass(_DestroyableMeta)):
    pass

T_co = TypeVar('T_co', bound='Destroyable', covariant=True)

class ArcMeta(GenericMeta, _DestroyableMeta):
    pass

class Arc(six.with_metaclass(ArcMeta, Generic[T_co], Destroyable)):
    pass