static getStyleAttributeFromElement_(cueElement, styles, attribute) {
    const TXml = shaka.util.TXml;
    const ttsNs = shaka.text.TtmlTextParser.styleNs_;

    // Styling on elements should take precedence
    // over the main styling attributes
    const elementAttribute = TXml.getAttributeNSList(
        cueElement,
        ttsNs,
        attribute);

    if (elementAttribute) {
      return elementAttribute;
    }
    return shaka.text.TtmlTextParser.getInheritedStyleAttribute_(
        cueElement, styles, attribute);
  }
Finds a specified attribute on the cue element and returns the value
if the attribute was found.

@param {!shaka.extern.xml.Node} cueElement
@param {!Array<!shaka.extern.xml.Node>} styles
@param {string} attribute
@return {?string}
@private