existingSequences
Returns a map with all the defined sequences that hold a relation to the specified tables in the database.
Note PostgreSQL is currently the only database that maps relational dependencies for sequences created when a SERIAL column is registered to an IdTable. Using this method with any other database returns an empty map.
Any sequence created using the CREATE SEQUENCE command will be ignored as it is not necessarily bound to any particular table. Sequences that are used in a table via triggers will also not be returned.