Belongs to type Data_Source_Property
String
Property type, e.g. `title`, `rich_text`, `number`, `select`, `multi_select`, `status`, `date`, `people`, `files`, `checkbox`, `url`, `email`, `phone_number`, `formula`, `relation`, `rollup`, `created_time`, `created_by`, `last_edited_time`, `last_edited_by`, `unique_id`.