code: def increment_lessons(self, measure_vals, reward_buff_sizes=None):
          
          ret = {}
          if reward_buff_sizes:
              for brain_name, buff_size in reward_buff_sizes.items():
                  if self._lesson_ready_to_increment(brain_name, buff_size):
                      measure_val = measure_vals[brain_name]
                      ret[brain_name] = (self.brains_to_curriculums[brain_name]
                                             .increment_lesson(measure_val))
          else:
              for brain_name, measure_val in measure_vals.items():
                  ret[brain_name] = (self.brains_to_curriculums[brain_name]
                                         .increment_lesson(measure_val))
          return ret
docs: Attempts to increments all the lessons of all the curriculums in this
          MetaCurriculum. Note that calling this method does not guarantee the
          lesson of a curriculum will increment. The lesson of a curriculum will
          only increment if the specified measure threshold defined in the
          curriculum has been reached and the minimum number of episodes in the
          lesson have been completed.
  
          Args:
              measure_vals (dict): A dict of brain name to measure value.
              reward_buff_sizes (dict): A dict of brain names to the size of their
                  corresponding reward buffers.
  
          Returns:
              A dict from brain name to whether that brain's lesson number was
              incremented.