Validate whether assessor in experiment_config is valid

def parse_assessor_content(experiment_config):
    '''Validate whether assessor in experiment_config is valid'''
    if experiment_config.get('assessor'):
        if experiment_config['assessor'].get('builtinAssessorName'):
            experiment_config['assessor']['className'] = experiment_config['assessor']['builtinAssessorName']
        else:
            validate_customized_file(experiment_config, 'assessor')