Initialization of the trainers
        :param trainer_config: The configurations of the trainers

def initialize_trainers(self, trainer_config: Dict[str, Dict[str, str]]):
        """
        Initialization of the trainers
        :param trainer_config: The configurations of the trainers
        """
        trainer_parameters_dict = {}
        for brain_name in self.external_brains:
            trainer_parameters = trainer_config['default'].copy()
            trainer_parameters['summary_path'] = '{basedir}/{name}'.format(
                basedir=self.summaries_dir,
                name=str(self.run_id) + '_' + brain_name)
            trainer_parameters['model_path'] = '{basedir}/{name}'.format(
                basedir=self.model_path,
                name=brain_name)
            trainer_parameters['keep_checkpoints'] = self.keep_checkpoints
            if brain_name in trainer_config:
                _brain_key = brain_name
                while not isinstance(trainer_config[_brain_key], dict):
                    _brain_key = trainer_config[_brain_key]
                for k in trainer_config[_brain_key]:
                    trainer_parameters[k] = trainer_config[_brain_key][k]
            trainer_parameters_dict[brain_name] = trainer_parameters.copy()
        for brain_name in self.external_brains:
            if trainer_parameters_dict[brain_name]['trainer'] == 'offline_bc':
                self.trainers[brain_name] = OfflineBCTrainer(
                    self.external_brains[brain_name],
                    trainer_parameters_dict[brain_name], self.train_model,
                    self.load_model, self.seed, self.run_id)
            elif trainer_parameters_dict[brain_name]['trainer'] == 'online_bc':
                self.trainers[brain_name] = OnlineBCTrainer(
                    self.external_brains[brain_name],
                    trainer_parameters_dict[brain_name], self.train_model,
                    self.load_model, self.seed, self.run_id)
            elif trainer_parameters_dict[brain_name]['trainer'] == 'ppo':
                self.trainers[brain_name] = PPOTrainer(
                    self.external_brains[brain_name],
                    self.meta_curriculum
                        .brains_to_curriculums[brain_name]
                        .min_lesson_length if self.meta_curriculum else 0,
                    trainer_parameters_dict[brain_name],
                    self.train_model, self.load_model, self.seed,
                    self.run_id)
                self.trainer_metrics[brain_name] = self.trainers[brain_name].trainer_metrics
            else:
                raise UnityEnvironmentException('The trainer config contains '
                                                'an unknown trainer type for '
                                                'brain {}'
                                                .format(brain_name))