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
}
	/**
	 * Sets the sort type, which indicates the way of sorting
	 * 
	 * @param sortType
	 *            sort type.
	 * @throws SemanticException
	 *             if the property is locked.
	 */
	public void setSortType( String sortType ) throws SemanticException
	{
		setStringProperty( GroupElement.SORT_TYPE_PROP, sortType );
	}
	/**
	 * Return the sort type.
	 * 
	 * @return the sort type.
	 */
	public String getSortType( )
	{
		return getStringProperty( GroupElement.SORT_TYPE_PROP );
	}
	/**
	 * Gets the on-prepare script of the group. Startup phase. No data binding
	 * yet. The design of an element can be changed here.
	 * 
	 * @return the on-prepare script of the group
	 * 
	 */
	public String getOnPrepare( )