Helper function used in service implementations to finish handling invocations of the <link linkend="gdbus-method-org-freedesktop-ModemManager1-Call.
SendDtmf">SendDtmf</link> D-Bus method. If you instead want to finish handling an invocation by returning an error,
use return_error or similar.
This method will free invocation, you cannot use it afterwards.
| this |
A GdbusCall. |
| invocation |