docs: def session(connection_string=None):
      """Gets a SQLAlchemy session"""
      global _session_makers
      connection_string = connection_string or oz.settings["db"]
  
      if not connection_string in _session_makers:
          _session_makers[connection_string] = sessionmaker(bind=engine(connection_string=connection_string))
  
      return _session_makers[connection_string]()