def get_collection_for_cls(self, cls):
        """
        Returns the collection name for a given document class.

        :param cls: The document class for which to return the collection name.

        :returns: The collection name for the given class.
        """
        if cls not in self.classes:
            if issubclass(cls, Document) and cls not in self.classes and cls not in self.deprecated_classes:
                self.autoregister(cls)
            else:
                raise AttributeError("Unknown object type: %s" % cls.__name__)
        collection = self.classes[cls]['collection']
        return collection
Returns the collection name for a given document class.

        :param cls: The document class for which to return the collection name.

        :returns: The collection name for the given class.