value or array of values, limit valid option arguments to a predefined set, see choices()
function, coerce or transform parsed command line values into another value, see coerce()
string or object, require certain keys not to be set, see conflicts()
value, set a default value for the option, see default()
string, the option description for help content, see describe()
string, the option description for help content, see describe()
string, the option description for help content, see describe()
string or object, require certain keys to be set, see implies()
boolean, apply path.normalize() to the option, see normalize()
string or array of strings, see
alias()