code: def log_state(self, state):
          
          results = []
          for field_idx, field in enumerate(self.fields):
              parent, stat = None, state
              for f in field:
                  parent, stat = stat, stat[f]
              results.append(stat)
          self.log(*results)
docs: Gathers the stats from self.trainer.stats and passes them into
              self.log, as a list