code: function addInterfaceMethod(interfaceName, funcName, fN) {
  
      // Store a reference to every interface/method
      if (Steam.INTERFACES[interfaceName] === undefined) {
          Steam.INTERFACES[interfaceName] = {};
      }
      Steam.INTERFACES[interfaceName][funcName] = fN;
  
      // Camel case the method name
      var name = funcName.substr(0,1).toLowerCase() + funcName.substr(1);
  
      // Add method to Steam's prototype
      if (!isMultiGameInterface(interfaceName)) {
          steam[name] = fN;
      }
      // If multiple interfaces use the same method name
      // Create a new method that requires a gameid property to find the correct method
      //  and call the steam method automatically
      else {
          // We only need to do this once
          if (steam[name] !== undefined) return;
  
          // e.g. Turns 'IEconItems_440' into 'IEconItems'
          var multi_interface_name = interfaceName.split('_')[0];
  
          // Add method to Steam's prototype
          steam[name] = function(steamObj, callback) {
              var gameid = get(this, steamObj, 'gameid');
  
              var interface_name = multi_interface_name + '_' + gameid;
  
              Steam.INTERFACES[interface_name][funcName].call(this, steamObj, callback);
          };
      }
  
  }
docs: Add some easy references to the new method