code: function ()
  	{
  		var nButton;
  
  		if ( typeof this.s.aoGroups != 'undefined' )
  		{
  			for ( var i=0, iLen=this.s.aoGroups.length ; i<iLen ; i++ )
  			{
  				nButton = this._fnDomGroupButton( i );
  				this.dom.groupButtons.push( nButton );
  				this.dom.buttons.push( nButton );
  				this.dom.collection.appendChild( nButton );
  			}
  		}
  	}
docs: Loop through the groups (provided in the settings) and create a button for each.
  @method  _fnAddgroups
  @returns void
  @private