Write the diff (toVol from fromVol) to the stream context manager.

def send(self, diff):
        """ Write the diff (toVol from fromVol) to the stream context manager. """
        if not self.dryrun:
            self._fileSystemSync()

        return self.butter.send(
            self.getSendPath(diff.toVol),
            self.getSendPath(diff.fromVol),
            diff,
            self.showProgress is True,
        )