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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def process_replay(self, controller, replay_data, map_data, player_id):
 """Process a single replay, updating the stats."""

    self._update_stage("start_replay")
    controller.start_replay(sc_pb.RequestStartReplay(
        replay_data=replay_data,
        map_data=map_data,
        options=interface,
        observed_player_id=player_id))

    feat = features.features_from_game_info(controller.game_info())

    self.stats.replay_stats.replays += 1
    self._update_stage("step")
    controller.step()
    while True:
      self.stats.replay_stats.steps += 1
      self._update_stage("observe")
      obs = controller.observe()

      for action in obs.actions:
        act_fl = action.action_feature_layer
        if act_fl.HasField("unit_command"):
          self.stats.replay_stats.made_abilities[
              act_fl.unit_command.ability_id] += 1
        if act_fl.HasField("camera_move"):
          self.stats.replay_stats.camera_move += 1
        if act_fl.HasField("unit_selection_point"):
          self.stats.replay_stats.select_pt += 1
        if act_fl.HasField("unit_selection_rect"):
          self.stats.replay_stats.select_rect += 1
        if action.action_ui.HasField("control_group"):
          self.stats.replay_stats.control_group += 1

        try:
          func = feat.reverse_action(action).function
        except ValueError:
          func = -1
        self.stats.replay_stats.made_actions[func] += 1

      for valid in obs.observation.abilities:
        self.stats.replay_stats.valid_abilities[valid.ability_id] += 1

      for u in obs.observation.raw_data.units:
        self.stats.replay_stats.unit_ids[u.unit_type] += 1

      for ability_id in feat.available_actions(obs.observation):
        self.stats.replay_stats.valid_actions[ability_id] += 1

      if obs.player_result:
        break

      self._update_stage("step")
      controller.step(FLAGS.step_mul)