code: function () { // eslint-disable-line object-shorthand
  			// Inits helper
  			helper.init(this);
  
  			// Check cli args for output format, and override on existance of string.
  			if (typeof pluginBuildFlag === 'string' || pluginBuildFlag instanceof String) {
  				helper.config.format = pluginBuildFlag;
  			}
  
  			// Fill summary array
  			this.book.summary.walk((article) => {
  				helper.summary.push(article);
  			});
  		}
docs: Gitbook hook on initilization.
  @memberOf module:index~hooks