code: def upgrade(cfg):
      
      db_node = cfg["db"]
      old_db_elems = ["host", "name", "port", "pass", "user", "dialect"]
      has_old_db_elems = [x in db_node for x in old_db_elems]
  
      if any(has_old_db_elems):
          print("Old database configuration found. "
                "Converting to new connect_string. "
                "This will *not* be stored in the configuration automatically.")
          cfg["db"]["connect_string"] = \
              "{dialect}://{user}:{password}@{host}:{port}/{name}".format(
                  dialect=cfg["db"]["dialect"]["value"],
                  user=cfg["db"]["user"]["value"],
                  password=cfg["db"]["pass"]["value"],
                  host=cfg["db"]["host"]["value"],
                  port=cfg["db"]["port"]["value"],
                  name=cfg["db"]["name"]["value"])
docs: Provide forward migration for configuration files.