code: function getIndexDetails(client, namespace, done) {
    var tasks = {
      client: attach.bind(null, client),
      namespace: attach.bind(null, namespace),
      getIndexes: ['client', 'namespace', getIndexes],
      getIndexStats: ['client', 'namespace', getIndexStats],
      getIndexSizes: ['client', 'namespace', getIndexSizes],
      indexes: [
        'getIndexes',
        'getIndexStats',
        'getIndexSizes',
        combineStatsAndIndexes
      ]
    };
  
    async.auto(tasks, function(err, results) {
      if (err) {
        // report error
        return done(err);
      }
      // all info was collected in indexes
      return done(null, results.indexes);
    });
  }
docs: get basic index information via `db.collection.indexes()`
  @param  {MongoClient} client      handle from mongodb driver
  @param  {String} namespace    namespace for which to get indexes
  @param  {Function} done       callback