docs: function(acl, callback) {
        var // This url should expire in one hour
          expiry = new Date(
            moment()
              .add(1, 'hour')
              .format(),
          ).getTime(),
          // Lets put together our policy
          stringPolicy =
            'PUT\n' +
            '\n' +
            '\n' +
            expiry +
            '\n' +
            'x-goog-acl:' +
            acl +
            '\n' +
            '/' +
            storageBucket +
            '/?defaultObjectAcl',
          // create signature and make it url safe
          signature = encodeURIComponent(
            crypto
              .createSign('sha256')
              .update(stringPolicy)
              .sign(privateKey, 'base64'),
          ),
          // signed url
          url =
            'https://' +
            storageBucket +
            '.storage.googleapis.com/?defaultObjectAcl&GoogleAccessId=' +
            googleServicesEmail +
            '&Expires=' +
            expiry +
            '&Signature=' +
            signature;
  
        rest
          .put(url, {
            headers: {
              'x-goog-acl': acl,
            },
          })
          .on('complete', function(err, res) {
            if (callback) callback();
          });
      }