code: public static BigtableInstanceClient createInstanceClient(BigtableOptions options)
        throws IOException, GeneralSecurityException {
      return new BigtableInstanceGrpcClient(createChannelPool(options.getAdminHost(), options));
    }
docs: Create a {@link BigtableInstanceClient}.  {@link BigtableSession} objects assume that
  {@link BigtableOptions} have a project and instance.  A {@link BigtableInstanceClient} does not
  require project id or instance id, so {@link BigtableOptions#getDefaultOptions()} may be used
  if there are no service account credentials settings.
  
  @return a fully formed {@link BigtableInstanceClient}
  @throws IOException
  @throws GeneralSecurityException