code: function delegateFilter(filterContext) {
      if (isFunction(filterContext.sourceValue)) {
          var func = filterContext.sourceValue;
          var source = filterContext.source;
          filterContext.sourceValue = function() {
              return fastApply(func, source, arguments);
          };
      }
      return true;
  }
docs: /*
  A filter which delegates methods calls from the target object
  to the source object.