Closes the current interchange by writing its footer segment.
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
The CreateInterchangeFooter method will write any existing segments to the output stream and then generate and write the interchange closing segment (IEA or UNZ). If there is an open transaction set, CreateInterchangeFooter will first call CreateTransactionFooter to close it. If there is an open functional group, CreateInterchangeFooter will first call CreateFunctionalGroupFooter to close it. If there is no interchange open, an exception will be thrown.