def _current_step_is_best(self, high):
    """Is the current step the best (highest if high, else lowest)."""
    metric = self._checkpoint_highest if high else self._checkpoint_lowest
    if metric is None:
      return False
    # History is a list of pairs (step, value).
    history = self._history.get('eval', 'metrics/' + metric)
    sequence = [float(i[1]) for i in history]  # Just the values.
    best = max(sequence) if high else min(sequence)  # Best value.
    last_is_best = float(history[-1][1]) == best  # Is last the best?
    cur_step = history[-1][0] == self._step  # Is last the current step?
    return cur_step and last_is_best
Is the current step the best (highest if high, else lowest).
trax/supervised/trainer_lib.py