Array is not null, the last entry in the array will be the property descriptor that describes the list property that is another list of items. 数组不为空,则该数组中的最后一项将为属性说明符,它描述作为另一个项列表的列表属性。
A null field descriptor is the descriptor that forms the blank division in export. 一个空白字段描述符是在输出中形成空格的描述符。