docs: public boolean isExcludeUnlistedClasses()
      {
          // The JAXB generated classes will return 'true' if the stanza was
          // specified, but without a value
          Boolean exclude = ivPUnit.isExcludeUnlistedClasses();
  
          // The version 2.0 persistence.xsd spelled out the default for
          // exclude-unlisted-classes is true (changed from version 1.0).
          //
          // This means there are 4 choices:
          //   <exclude-unlisted-classes> not specified                   --> Not excluded
          //   <exclude-unlisted-classes>false</exclude-unlisted-classes> --> Not excluded
          //   <exclude-unlisted-classes>true</exclude-unlisted-classes>  --> Excluded
          //   <exclude-unlisted-classes/>                                --> Excluded
          //
          // The last choice matches the sample's implied semantics.
  
          // The default when not present at all is 'false'
          if (exclude == null)
          {
              exclude = Boolean.FALSE;
  
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                  Tr.debug(tc, "isExcludeUnlistedClasses : defaulted to FALSE");
          }
  
          return exclude.booleanValue();
      }