code: function becomeMaster(provider, bigIp, options) {
          let hasUcs = false;
  
          logger.info('Becoming master.');
          logger.info('Checking for backup UCS.');
  
          return provider.getStoredUcs()
              .then((response) => {
                  if (response) {
                      hasUcs = true;
                      return loadUcs(provider, bigIp, response, options.cloud);
                  }
                  return q();
              })
              .then(() => {
                  // If we loaded UCS, re-initialize encryption so our keys
                  // match each other
                  if (hasUcs) {
                      return initEncryption.call(this, provider, bigIp);
                  }
                  return q();
              })
              .then(() => {
                  return bigIp.list('/tm/sys/global-settings');
              })
              .then((globalSettings) => {
                  const hostname = globalSettings ? globalSettings.hostname : undefined;
  
                  if (hostname) {
                      this.instance.hostname = hostname;
                  } else {
                      logger.debug('hostname not found in this.instance or globalSettings');
                  }
  
                  return bigIp.list('/tm/sys/provision');
              })
              .then((response) => {
                  const modulesProvisioned = {};
  
                  if (response && response.length > 0) {
                      response.forEach((module) => {
                          modulesProvisioned[module.name] = !(module.level === 'none');
                      });
                  }
  
                  // Make sure device group exists
                  logger.info('Creating device group.');
  
                  const deviceGroupOptions = {
                      autoSync: options.autoSync,
                      saveOnAutoSync: options.saveOnAutoSync,
                      fullLoadOnSync: options.fullLoadOnSync,
                      asmSync: modulesProvisioned.asm || options.asmSync,
                      networkFailover: options.networkFailover
                  };
  
                  return bigIp.cluster.createDeviceGroup(
                      options.deviceGroup,
                      'sync-failover',
                      [this.instance.hostname],
                      deviceGroupOptions
                  );
              })
              .then(() => {
                  logger.info('Writing master file.');
                  return writeMasterFile(hasUcs);
              });
      }
docs: Handles becoming master.
  
  @returns {Promise} promise which is resolved tieh true if successful