code: func (c *CountingWriter) WriteByte(b byte) error {
  	// If our underlying Writer is a ByteWriter, use its WriteByte directly.
  	if bw, ok := c.Writer.(io.ByteWriter); ok {
  		if err := bw.WriteByte(b); err != nil {
  			return err
  		}
  		c.Count++
  		return nil
  	}
  
  	c.singleByteBuf[0] = b
  	_, err := c.Write(c.singleByteBuf[:])
  	return err
  }
docs: // WriteByte implements io.ByteWriter.