Bug 167545 Copy a cascading parameter group and paste it to another parameter group causes an exception thrown
Steps to reproduce: 1.Copy a cascading parameter group using short cut key "Ctrl+x"/"Ctrl+c", or choosing context menu "Cut"/"Copy"; 2.Paste it to another parameter group using short cut key "Ctrl+v", or choosing context menu "Paste"; Expected result: The source one is pasted in the destination. Actual result: An exception thrown org.eclipse.birt.report.model.api.command.ContentException: The Cascading Parameter Group("Source") is not allowed in the slot (parameters) of Parameter Group("Destination").
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
*/
	public static List getDataSets( )
	{
		return SessionHandleAdapter.getInstance( )
				.getReportDesignHandle( )
				.getVisibleDataSets( );
	}
	public static Iterator getThemes( )
	{
		return getThemes( new AlphabeticallyComparator( ) );
	}
	private static Iterator getThemes( AlphabeticallyComparator comparator )
	{
		List themes = SessionHandleAdapter.getInstance( )
				.getReportDesignHandle( )
				.getVisibleThemes( IAccessControl.DIRECTLY_INCLUDED_LEVEL );
		Object[] themesArray = themes.toArray( );
		if ( comparator != null )
		{
			Arrays.sort( themesArray, comparator );
		}
		return Arrays.asList( themesArray ).iterator( );
	}
	/**
	 * Generates GroupElementHandle for given model list.
	 * 
	 * @param modelList
	 * @return
	 */
	public static GroupElementHandle getGroupElementHandle( List modelList )