Add separate ConcatenationSubset impl file
Add separate ConcatenationSubset impl file

briadam/queso,roystgnr/queso,roystgnr/queso,briadam/queso,briadam/queso,briadam/queso,roystgnr/queso,roystgnr/queso,roystgnr/queso,roystgnr/queso,briadam/queso