n.<DD><CODE>base</CODE> - the base URI the uri was resolved from.<DD><CODE>validator</CODE> - a validator that can be used to revalidate an existing
 cached source at the URI. Can be null if there is no cached source 
 available.
<DT><B>Returns:</B><DD>the loaded module script, or null if it can't be found, or 
 <A HREF="../../../../../../org/mozilla/javascript/commonjs/module/provider/ModuleSourceProvider.html#NOT_MODIFIED"><CODE>ModuleSourceProvider.NOT_MODIFIED</CODE></A> if it revalidated the existing 
