docs: function moduleSize(id, paths) {
      var path = id;
      var extension = '.js';
      // Use `paths:` to resolve an alias.
      if (paths[id]) {
          path = paths[id];
      }
      // Does the dependency reference a plugin?
      if (path.indexOf('!') !== -1) {
          // Split into plugin and path.
          var pathParts = path.split('!');
          // Often, the plugin maps to the extension it handles.
          extension = '.' + pathParts[0];
          path = pathParts[1];
      }
      // Try to get the file at the path.
      var stats;
      try {
          stats = fs.statSync(path);
          return stats['size'];
      }
      catch(e) {}
  
      // Didn't find it? Let's try again with the extension added.
      if (path.slice(-extension.length) !== extension) {
          path = path + extension;
      }
      try {
          stats = fs.statSync(path);
          return stats['size'];
      }
      catch(e) {}
  
      // Still didn't find the file.
      return null;
  }