add test for duplicate prefLabel in different vocabs (valid)
add test for duplicate prefLabel in different vocabs (valid)

jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry,jonphipps/Metadata-Registry