code: func (f *Fpdf) outbuf(r io.Reader) {
  	if f.state == 2 {
  		f.pages[f.page].ReadFrom(r)
  		f.pages[f.page].WriteString("\n")
  	} else {
  		f.buffer.ReadFrom(r)
  		f.buffer.WriteString("\n")
  	}
  }
docs: // outbuf adds a buffered line to the document