Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'folders') and self.folders is not None:
            _dict['folders'] = [x._to_dict() for x in self.folders]
        if hasattr(self, 'objects') and self.objects is not None:
            _dict['objects'] = [x._to_dict() for x in self.objects]
        if hasattr(self,
                   'site_collections') and self.site_collections is not None:
            _dict['site_collections'] = [
                x._to_dict() for x in self.site_collections
            ]
        if hasattr(self, 'urls') and self.urls is not None:
            _dict['urls'] = [x._to_dict() for x in self.urls]
        if hasattr(self, 'buckets') and self.buckets is not None:
            _dict['buckets'] = [x._to_dict() for x in self.buckets]
        if hasattr(self,
                   'crawl_all_buckets') and self.crawl_all_buckets is not None:
            _dict['crawl_all_buckets'] = self.crawl_all_buckets
        return _dict