/**
  * Sets line transparency
  * @see Cpdf::setLineTransparency()
  *
  * Valid blend modes are (case-sensitive):
  *
  * Normal, Multiply, Screen, Overlay, Darken, Lighten,
  * ColorDodge, ColorBurn, HardLight, SoftLight, Difference,
  * Exclusion
  *
  * @param string $mode the blending mode to use
  * @param float $opacity 0.0 fully transparent, 1.0 fully opaque
  */
 protected function _set_line_transparency($mode, $opacity)
 {
     $this->_pdf->setLineTransparency($mode, $opacity);
 }