The value is an NSCharacterSet object.
The character set is used to determine the terminating character for a tab column. The tab and newline characters are implied even if they don’t exist in the character set. This attribute is optional.
Available in Mac OS X v10.3 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)