Closes any open Twain Data Source.
Synopsis
error = TwainCloseSource()
Returns
An empty string if the data source is successfully closed, or an error code not.
Notes
It is not considered an error to call TwainCloseSource if the data source manager is not open, or no data source is currently open.
If you do not call TwainCloseSource, then when your main script ends, RXTWAIN.DLL will automatically close any open data source for you. So cleanup is done automatically when your main script ends.