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
*/
	public void setIntervalRange( double intervalRange )
			throws SemanticException
	{
		setFloatProperty( GroupElement.INTERVAL_RANGE_PROP, intervalRange );
	}
	/**
	 * Returns the sort direction of this group. The return value is defined in
	 * <code>DesignChoiceConstants</code> and can be one of:
	 * 
	 * <ul>
	 * <li><code>SORT_DIRECTION_ASC</code>
	 * <li><code>SORT_DIRECTION_DESC</code>
	 * 
	 * </ul>
	 * 
	 * @return the sort direction of this group
	 */
	public String getSortDirection( )
	{
		return getStringProperty( GroupElement.SORT_DIRECTION_PROP );
	}
	/**
	 * Sets the sort direction of this group. The return value is defined in
	 * <code>DesignChoiceConstants</code> and can be one of:
	 * 
	 * <ul>
	 * <li><code>SORT_DIRECTION_ASC</code>
	 * <li><code>SORT_DIRECTION_DESC</code>
	 *