docs: def send(self, diff):
          """ Return Context Manager for a file-like (stream) object to send a diff. """
          if Store.skipDryRun(logger, self.dryrun)("send %s", diff):
              return None
  
          (diffTo, diffFrom) = self.toArg.diff(diff)
          self._client.send(diffTo, diffFrom)
  
          progress = DisplayProgress(diff.size) if self.showProgress is True else None
          return _SSHStream(self._client, progress)