PR03: Test the parsing and semantics of sections. 4. Test first section of document is not A. @B@ 1. Test section with no name. @A This section has no name. @$@@{Walrus@} 2. Test section with a name @A@ 3. Test the entire hierarchy. @A@ @B@ @C@ @D@ @E@ 5. Test detection of discontinuity in levels. @A@ @C@ @E@ @A@ @B@ @D@