g should occur and an optional target.

        Note that without a target being set either here or via setTarget(),
        a MemoryHandler is no use to anyone!

        The ``flushOnClose`` argument is ``True`` for backward compatibility
        reasons - the old behaviour is that when the handler is closed, the
        buffer is flushed, even if the flush level hasn't been exceeded nor the
        capacity exceeded. To prevent this, set ``flushOnClose`` to ``False``.
        N)