Try handling unclosed sql connections by calling dispose on the engine before it is put back into the pool.

cdplib/db_handlers/SQLHandler.py

@@ -48,7 +48,6 @@ class SQLHandler:
     closing of a database connection,
      this avoids errors when parallelizing with multiprocessing.
     '''
-    pass
     def __init__(self, db_uri: str = None,
                  is_case_insensitive: bool = False):
         '''