Free global annotation memory.

def free_memory(cls, exclude=None):
        """Free global annotation memory."""

        annotations_in_memory = Annotation.__ANNOTATIONS_IN_MEMORY__

        exclude = () if exclude is None else exclude

        for annotation_cls in list(annotations_in_memory.keys()):

            if issubclass(annotation_cls, exclude):
                continue

            if issubclass(annotation_cls, cls):
                del annotations_in_memory[annotation_cls]