'Resolves the class model attribute if it\'s a string and returns it.'

@classmethod
def get_registered_models(cls):

    if (cls.model is None):
        if (u'model' in cls.__dict__):
            return []
        else:
            raise ValueError((u'You    must    set    the    model    attribute    on    Binding    %r!' % cls))
    if ((cls.fields is None) and (cls.exclude is None)):
        raise ValueError((u'You    must    set    the    fields    or    exclude    attribute    on    Binding    %r!' % cls))
    if isinstance(cls.model, six.string_types):
        cls.model = apps.get_model(cls.model)
    cls.model_label = (u'%s.%s' % (cls.model._meta.app_label.lower(), cls.model._meta.object_name.lower()))
    return [cls.model]
