code: function oldIsPlugin (nodeModulePath) {
            // then check if the npm module is one plugin
            try {
              if (fs.statSync( path.resolve( nodeModulePath, 'plugin.js' ) )) {
                return true;
              } else {
                return false;
              }
            } catch (e) {
              return false;
            }
          }
docs: old we.js is plugin function to check is one npm module is plugin