code: func (c *Client) bundleRPC(ctx context.Context, opts []grpc.CallOption, req *s.BatchRequest_Entry) (*s.BatchResponse_Entry, error) {
  	c.initBundler()
  
  	be := &batchEntry{
  		req:      req,
  		ctx:      ctx,
  		opts:     opts,
  		complete: make(chan *s.BatchResponse_Entry, 1),
  	}
  	if err := c.addEntry(be); err != nil {
  		return nil, err
  	}
  
  	resp := <-be.complete
  	if e := resp.GetErr(); e != nil {
  		return nil, e.ToError()
  	}
  	return resp, nil
  }
docs: // bundleRPC adds req to the underlying Bundler, blocks until it completes, and
  // returns its response.