def implementedByFallback(cls):
    """Return the interfaces implemented for a class' instances

      The value returned is an IDeclaration.
    """
    try:
        spec = cls.__dict__.get('__implemented__')
    except AttributeError:

        # we can't get the class dict. This is probably due to a
        # security proxy.  If this is the case, then probably no
        # descriptor was installed for the class.

        # We don't want to depend directly on zope.security in
        # zope.interface, but we'll try to make reasonable
        # accommodations in an indirect way.

        # We'll check to see if there's an implements:

        spec = getattr(cls, '__implemented__', None)
        if spec is None:
            # There's no spec stred in the class. Maybe its a builtin:
            spec = BuiltinImplementationSpecifications.get(cls)
            if spec is not None:
                return spec
            return _empty

        if spec.__class__ == Implements:
            # we defaulted to _empty or there was a spec. Good enough.
            # Return it.
            return spec

        # TODO: need old style __implements__ compatibility?
        # Hm, there's an __implemented__, but it's not a spec. Must be
        # an old-style declaration. Just compute a spec for it
        return Declaration(*_normalizeargs((spec, )))

    if isinstance(spec, Implements):
        return spec

    if spec is None:
        spec = BuiltinImplementationSpecifications.get(cls)
        if spec is not None:
            return spec

    # TODO: need old style __implements__ compatibility?
    if spec is not None:
        # old-style __implemented__ = foo declaration
        spec = (spec, ) # tuplefy, as it might be just an int
        spec = Implements(*_normalizeargs(spec))
        spec.inherit = None    # old-style implies no inherit
        del cls.__implemented__ # get rid of the old-style declaration
    else:
        try:
            bases = cls.__bases__
        except __HOLE__:
            if not callable(cls):
                raise TypeError("ImplementedBy called for non-factory", cls)
            bases = ()

        spec = Implements(*[implementedBy(c) for c in bases])
        spec.inherit = cls

    spec.__name__ = (getattr(cls, '__module__', '?') or '?') + \
                    '.' + (getattr(cls, '__name__', '?') or '?')

    try:
        cls.__implemented__ = spec
        if not hasattr(cls, '__providedBy__'):
            cls.__providedBy__ = objectSpecificationDescriptor

        if (isinstance(cls, DescriptorAwareMetaClasses)
            and
            '__provides__' not in cls.__dict__):
            # Make sure we get a __provides__ descriptor
            cls.__provides__ = ClassProvides(
                cls,
                getattr(cls, '__class__', type(cls)),
                )

    except TypeError:
        if not isinstance(cls, type):
            raise TypeError("ImplementedBy called for non-type", cls)
        BuiltinImplementationSpecifications[cls] = spec

    return spec
dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/zope/interface/declarations.py/implementedByFallback