code: protected ManagedChannel createChannelPool(final ChannelPool.ChannelFactory channelFactory, int count)
        throws IOException {
      return new ChannelPool(channelFactory, count);
    }
docs: Create a new {@link com.google.cloud.bigtable.grpc.io.ChannelPool}, with auth headers.  This
  method allows users to override the default implementation with their own.
  
  @param channelFactory a {@link ChannelPool.ChannelFactory} object.
  @param count The number of channels in the pool.
  @return a {@link com.google.cloud.bigtable.grpc.io.ChannelPool} object.
  @throws java.io.IOException if any.