def _add_tasks_to_taskpaper(
        self,
        pathToTaskpaperDoc,
        taskString
    ):
        """*add the tasks to a taskpaper document*

        **Key Arguments:**
            - ``pathToTaskpaperDoc`` -- the path to the taskpaper document to import the tasks into
            - ``taskString`` -- a string containing tasks in taskpaper format
        """
        self.log.info('starting the ``_add_tasks_to_taskpaper`` method')

        exists = os.path.exists(pathToTaskpaperDoc)
        thisData = ""
        if exists:
            try:
                self.log.debug("attempting to open the file %s" %
                               (pathToTaskpaperDoc,))
                readFile = codecs.open(
                    pathToTaskpaperDoc, encoding='utf-8', mode='r')
                thisData = readFile.read()
                readFile.close()
            except IOError, e:
                message = 'could not open the file %s' % (pathToTaskpaperDoc,)
                self.log.critical(message)
                raise IOError(message)
            readFile.close()

        thisData = taskString + "\n" + thisData

        try:
            self.log.debug("attempting to open the file %s" %
                           (pathToTaskpaperDoc,))
            writeFile = codecs.open(
                pathToTaskpaperDoc, encoding='utf-8', mode='w')
        except IOError, e:
            message = 'could not open the file %s' % (pathToTaskpaperDoc,)
            self.log.critical(message)
            raise IOError(message)
        writeFile.write(thisData)
        writeFile.close()

        ws = workspace(
            log=self.log,
            settings=self.settings,
            fileOrWorkspacePath=pathToTaskpaperDoc
        )
        ws.sort()

        self.log.info('completed the ``_add_tasks_to_taskpaper`` method')
        return None