These lemmas allow merging a sepL "into" a separate sepL2 if it iterates over one of the 2 lists of the sepL2. Also added some helper lemmas to relate "sepL2 where one list is ignored" with sepL.
These lemmas allow merging a sepL "into" a separate sepL2 if it iterates over one of the 2 lists of the sepL2. Also added some helper lemmas to relate "sepL2 where one list is ignored" with sepL.