Item blocks.
Optional has_True, if the item has a checkbox.
Optional is_True, if the item is checked.
Type of the item numbering type; must be one of "a" for a lowercase letter, "A" for an uppercase letter, "i" for lowercase Roman numerals, "I" for uppercase Roman numerals, "1" for decimal numbers, or empty for unordered lists.
Value of the item; pass 0 for unordered lists.
Describes an item of a list page block to be sent.