code: func (f *Fpdf) Ln(h float64) {
  	f.x = f.lMargin
  	if h < 0 {
  		f.y += f.lasth
  	} else {
  		f.y += h
  	}
  }
docs: // Ln performs a line break. The current abscissa goes back to the left margin
  // and the ordinate increases by the amount passed in parameter. A negative
  // value of h indicates the height of the last printed cell.
  //
  // This method is demonstrated in the example for MultiCell.