code: def get_course_grade(self, course_id, username):
          
          results = self.client.courses(course_id).get(username=username)
          for row in results:
              if row.get('username') == username:
                  return row
  
          raise HttpNotFoundError('No grade record found for course={}, username={}'.format(course_id, username))
docs: Retrieve the grade for the given username for the given course_id.
  
          Args:
          * ``course_id`` (str): The string value of the course's unique identifier
          * ``username`` (str): The username ID identifying the user for which to retrieve the grade.
  
          Raises:
  
          HttpNotFoundError if no grade found for the given user+course.
  
          Returns:
  
          a dict containing:
  
          * ``username``: A string representation of a user's username passed in the request.
          * ``course_key``: A string representation of a Course ID.
          * ``passed``: Boolean representing whether the course has been passed according the course's grading policy.
          * ``percent``: A float representing the overall grade for the course
          * ``letter_grade``: A letter grade as defined in grading_policy (e.g. 'A' 'B' 'C' for 6.002x) or None