code: function(config) {
      var directory = null;
  
      if(config.workingDir) {
         directory = path.join(config.workingDir, 'level'); 
      } else {
          throw Errors.invalidConfig('Invalid configuration. Working directory not defined.');
      }
      
      return directory;
  }
docs: Get level directory
  @param config
  @result string
  @throws Error