Extract notebook text (instructions).

        @param element_id: Element id to extract notebook links.
        @type element_id: str

        @return: Notebook URL.
        @rtype: [str]

def _extract_notebook_text(self, element_id):
        """
        Extract notebook text (instructions).

        @param element_id: Element id to extract notebook links.
        @type element_id: str

        @return: Notebook URL.
        @rtype: [str]
        """
        headers = self._auth_headers_with_json()
        data = {'courseId': self._course_id,
                'learnerId': self._user_id, 'itemId': element_id}
        dom = get_page(self._session, OPENCOURSE_NOTEBOOK_LAUNCHES,
                       post=True,
                       json=True,
                       user_id=self._user_id,
                       course_id=self._course_id,
                       headers=headers,
                       element_id=element_id,
                       data=json.dumps(data)
                       )

        # Return authorization id. This id changes on each request
        return dom['elements'][0]['authorizationId']