function Group() {
    this.__group = true;

    /**
     * Grouping level, starting with 0.
     * @property level
     * @type {Number}
     */
    this.level = 0;

    /***
     * Number of rows in the group.
     * @property count
     * @type {Integer}
     */
    this.count = 0;

    /***
     * Grouping value.
     * @property value
     * @type {Object}
     */
    this.value = null;

    /***
     * Formatted display value of the group.
     * @property title
     * @type {String}
     */
    this.title = null;

    /***
     * Whether a group is collapsed.
     * @property collapsed
     * @type {Boolean}
     */
    this.collapsed = false;

    /***
     * GroupTotals, if any.
     * @property totals
     * @type {GroupTotals}
     */
    this.totals = null;

    /**
     * Rows that are part of the group.
     * @property rows
     * @type {Array}
     */
    this.rows = [];

    /**
     * Sub-groups that are part of the group.
     * @property groups
     * @type {Array}
     */
    this.groups = null;

    /**
     * A unique key used to identify the group.  This key can be used in calls to DataView
     * collapseGroup() or expandGroup().
     * @property groupingKey
     * @type {Object}
     */
    this.groupingKey = null;
  }
Information about a group of rows.
@class Group
@extends Slick.NonDataItem
@constructor