'When `depth` is specified as a Factory parameter, creates a
tree of children with that many levels.'

@post_generation
def depth(self, create, depth, **kwargs):

    if (depth == 0):
        self.load_item.side_effect = (lambda x: LeafModuleFactory(descriptor_cls=HtmlDescriptor))
    else:
        self.load_item.side_effect = (lambda x: ContainerModuleFactory(descriptor_cls=VerticalBlock, depth=(depth - 1)))
