code: func CopyBatch(dst BatchWriter, src Reader, batchSize int) (cnt int, err error) {
  	if batchSize <= 0 {
  		batchSize = DefaultBatch
  	}
  	buf := make([]Quad, batchSize)
  	bsrc, ok := src.(BatchReader)
  	if !ok {
  		bsrc = batchReader{src}
  	}
  	var n int
  	for err == nil {
  		n, err = bsrc.ReadQuads(buf)
  		if err != nil && err != io.EOF {
  			return
  		}
  		eof := err == io.EOF
  		n, err = dst.WriteQuads(buf[:n])
  		cnt += n
  		if eof {
  			break
  		}
  	}
  	return
  }
docs: // CopyBatch will copy all quads from src to dst in a batches of batchSize.
  // It returns copied quads count and an error, if it failed.
  //
  // If batchSize <= 0 default batch size will be used.