Bug 181121 Model should provide utility method for cube to get correspond dimension key.
In model cube handle, the relation of cube data set and dimension data sets are managed by a series of dimension condition handles.We need model to add utility method so that we can easily get corresponding dimension data set column names according to given cube dimension keys.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/PropertyStructure.java
}
		return clone;
	}
	/**
	 * Clone the structure list, a list value contains a list of structures.
	 * 
	 * @param list
	 *            The structure list to be cloned.
	 * @return The cloned structure list.
	 */
	private ArrayList cloneStructList( ArrayList list )
	{
		if ( list == null )
			return null;
		ArrayList returnList = new ArrayList( );
		for ( int i = 0; i < list.size( ); i++ )
		{
			Object item = list.get( i );
			if ( item instanceof Structure )
			{
				returnList.add( ( (Structure) item ).copy( ) );
			}
			else
			{
				assert false;
			}
		}
		return returnList;
	}
}