Either NULL or a UTF-8 string (representable in the target encoding) to convert and output in place of characters that cannot be represented in the target encoding. NULL means use \u1234 or \U12345678 format.
The time the output was last updated. This must be set on object construction and represents the timestamp to put on the resulting file or #GsfOutfile member. Not all derived classes will actually do anything with this property.
The container, optionally %NULL, in which this output lives.