Extract assignment text (instructions).

        @param element_id: Element id to extract assignment instructions from.
        @type element_id: str

        @return: List of assignment text (instructions).
        @rtype: [str]

def _extract_assignment_text(self, element_id):
        """
        Extract assignment text (instructions).

        @param element_id: Element id to extract assignment instructions from.
        @type element_id: str

        @return: List of assignment text (instructions).
        @rtype: [str]
        """
        dom = get_page(self._session, OPENCOURSE_PROGRAMMING_ASSIGNMENTS_URL,
                       json=True,
                       course_id=self._course_id,
                       element_id=element_id)

        return [element['submissionLearnerSchema']['definition']
                ['assignmentInstructions']['definition']['value']
                for element in dom['elements']]