docs: function getter() {
  
        // not found
        var cached = internalCache[filename];
        if (!cached) {
          return undefined;
        }
        // we have already tested whether the cached value is valid and deleted it if not
        else if (isTestedCache[filename]) {
          return cached.output;
        }
        // test the input
        else {
          var isMatch = cached.input && fs.existsSync(filename) &&
            (cached.input === fs.readFileSync(filename).toString());
          isTestedCache[filename] = true;
          internalCache[filename] = isMatch && cached;
          return getter();
        }
      }