docs: function getById(hypemId, callback) {
          var options = {
              method: 'HEAD',
              url: HYPEM_GO_URL + hypemId,
              followRedirect: false,
              timeout: FIVE_SECONDS_IN_MILLIS
          };
  
          request(options, function (error, response) {
              if (error || response.statusCode !== 302) {
                  callback(error, null);
                  return;
              }
              var songUrl = response.headers.location;
              if (isSoundcloudUrl(songUrl)) {
                  var soundcloudUrl = getNormalizedSoundcloudUrl(songUrl);
                  callback(null, soundcloudUrl);
              } else {
                  requestHypemKey(hypemId, function (error, hypemKey) {
                      if (error) {
                          callback(error, null);
                          return;
                      }
                      requestMp3Url(hypemId, hypemKey, callback);
                  });
              }
          });
      }