<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def register(self, name, content, description=None):
 """ Register a new document. :param content: Content of this document. Jinja and rst are supported. :type content: str :param name: Unique name of the document for documentation purposes. :param description: Short description of this document """

        return self.__app.documents.register(name, content, self._plugin, description)