OptionalcountHow many cells hold it, when the host knows.
OptionalkeyThe identity a check is kept by, when two rows may show the same text (by value, the number
1 and the text '1). Defaults to text.
The value as shown, and the identity a check is kept by unless key says otherwise.
OptionalvalueThe value the text stands for, when a host needs it back (a filter writes it).
One value the checklist offers.