How to use the bunyan.levelFromName function in bunyan

name: DEFAULT_LOGGER_NAME,
      streams: [{
        type: 'raw',
        name: 'ConsoleLogStream',
        stream: new ConsoleLogStream({formatter: LogFormatter}),
        level: 'info'
      }],
      level: 'info'
    };
    this.rootLogger = new Logger(rootLoggerOptions);

    this._bindNodeLoggerMethods(this.rootLogger);
    this._cleanLoggersInterval = null;

    this.nameFromLevel = bunyan.nameFromLevel;
    this.levelFromName = bunyan.levelFromName;
    this.DEFAULT_LOGGER_NAME = DEFAULT_LOGGER_NAME;

    // in case the node we're running has it's own logging system, we'll
    // allow users to pass in callbacks for getting and setting loggers
    // through the logging services (_handleGetLoggers, _handleSetLoggerLevel)
    this._externalLog = {
      getLoggers: null,
      setLoggerLevel: null
    };

    KNOWN_LOGS.forEach((log) => {
      this.generateLogger(log);
    });
  }

'use strict';

const bunyan = require('bunyan');
const Hoek = require('hoek');
const Joi = require('joi');

/**
 * @constant {array} availableLevels - List of available Bunyan log levels
 * @private
 */
const availableLevels = Object.keys(bunyan.levelFromName);
/**
 * @constant {object} schema - Validation schema
 * @private
 */
const schema = {
  levels: {
    ops: Joi.string().valid(availableLevels),
    response: Joi.string().valid(availableLevels),
    error: Joi.string().valid(availableLevels),
    log: Joi.string().valid(availableLevels),
    request: Joi.string().valid(availableLevels)
  },
  logger: Joi.object().required(),
  formatters: Joi.object()
};

constructor () {
    Object.keys(bunyan.levelFromName).forEach((level) => {
      this[level] = function () {
        process.send({type: 'log', level, arguments: Array.from(arguments)})
      }

      this[`sys${level.charAt(0).toUpperCase()}${level.slice(1)}`] = function () {
        process.send({type: 'systemLog', level, arguments: Array.from(arguments)})
      }
    })
  }
}