code: function makeSubclass(getSignatureFunction) {
          var superClass = OAuth.SignatureMethod;
          var subClass = function() {
              superClass.call(this);
          };
          subClass.prototype = new superClass();
          // Delete instance variables from prototype:
          // delete subclass.prototype... There aren't any.
          subClass.prototype.getSignature = getSignatureFunction;
          subClass.prototype.constructor = subClass;
          return subClass;
      }
docs: Create a subclass of OAuth.SignatureMethod, with the given getSignature function.