Bug 160176 Create design by a template
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignSession.java
* @param module
	 *            the module to drop
	 */
	public void drop( Module module )
	{
		if ( module instanceof ReportDesign )
		{
			assert designs.contains( module );
			designs.remove( module );
		}
		else if ( module instanceof Library )
		{
			assert libraries.contains( module );
			libraries.remove( module );
		}
	}
	/**
	 * Returns the application units. The return value is defined in
	 * <code>DesignChoiceConstants</code> and is one of:
	 * 
	 * <ul>
	 * <li><code>UNITS_IN</code></li>
	 * <li><code>UNITS_CM</code></li>
	 * <li><code>UNITS_MM</code></li>
	 * <li><code>UNITS_PT</code></li>
	 * <li><code>UNITS_PC</code></li>
	 * </ul>
	 * 
	 * @return the application units as a string
	 *