code: function getOpacityOverride(sceneDrawGroup, isFill) {
      var opacity;
      if (isFill) {
          opacity = sceneDrawGroup._hidden['opacity:fill'];
      } else {
          opacity = sceneDrawGroup._hidden['opacity:outline'];
      }
      if (sceneDrawGroup._hidden['opacity:general'] !== undefined) {
          opacity = sceneDrawGroup._hidden['opacity:general'];
      }
      return opacity;
  }
docs: Returns the final opacity override selecting between fill-opacity and outline-opacity. Returned value can be a float or a function string to be called at Tangram's runtime if the override is active A falseable value will be returned if the override is not active