Bug 161174 Expect to set/get interval range with a 'String' param in GroupHandle.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/GroupHandle.java
* </ul>
	 * 
	 * @param direction
	 *            the sort direction of this group
	 * @throws SemanticException
	 *             if the property is locked or the input value is not one of
	 *             the above.
	 * 
	 */
	public void setSortDirection( String direction ) throws SemanticException
	{
		setStringProperty( GroupElement.SORT_DIRECTION_PROP, direction );
	}
	/**
	 * Checks whether the group header slot is empty.
	 * 
	 * @return true is the header slot is not empty, otherwise, return false.
	 * 
	 */
	public boolean hasHeader( )
	{
		return ( getHeader( ).getCount( ) != 0 );
	}
	/**
	 * Checks whether the group footer slot is empty.
	 * 
	 * @return true is the footer slot is not empty, otherwise, return false.
	 * 
	 */
	public boolean hasFooter( )