code: function getFoldOnLine(cm, line) {
          var pos = CodeMirror.Pos(line, 0);
          var folds = cm.findMarksAt(pos) || [];
          folds = folds.filter(isFold);
          return folds.length ? folds[0] : undefined;
      }
docs: Helper function to return the fold text marker on a line in an editor
  @param   {CodeMirror} cm   The CodeMirror instance for the active editor
  @param   {Number}     line The line number representing the position of the fold marker
  @returns {TextMarker} A CodeMirror TextMarker object