function _isCurrentlyFolded(line) {
            var keys = Object.keys(cm._lineFolds), i = 0, range;
            while (i < keys.length) {
                range = cm._lineFolds[keys[i]];
                if (range.from.line < line && range.to.line >= line) {
                    return range;
                }
                i++;
            }
        }
@private
helper function to check if the given line is in a folded region in the editor.
@param {number} line the
@return {Object} the range that hides the specified line or undefine if the line is not hidden