code: function(module, exports) {
  
  	'use strict';
  
  	module.exports = function only_once(fn) {
  	    return function() {
  	        if (fn === null) throw new Error('Callback was already called.');
  	        fn.apply(this, arguments);
  	        fn = null;
  	    };
  	};
  
  
  /***/ }
docs: /* 10