code: private static CmsXmlContentDefinition getCachedContentDefinition(String schemaLocation, EntityResolver resolver) {
  
          if (resolver instanceof CmsXmlEntityResolver) {
              // check for a cached version of this content definition
              CmsXmlEntityResolver cmsResolver = (CmsXmlEntityResolver)resolver;
              return cmsResolver.getCachedContentDefinition(schemaLocation);
          }
          return null;
      }
docs: Looks up the given XML content definition system id in the internal content definition cache.<p>
  
  @param schemaLocation the system id of the XML content definition to look up
  @param resolver the XML entity resolver to use (contains the cache)
  
  @return the XML content definition found, or null if no definition is cached for the given system id