code: def engine(self):
          
          pid = os.getpid()
          conn = SQLAlchemyTarget._engine_dict.get(self.connection_string)
          if not conn or conn.pid != pid:
              # create and reset connection
              engine = sqlalchemy.create_engine(
                  self.connection_string,
                  connect_args=self.connect_args,
                  echo=self.echo
              )
              SQLAlchemyTarget._engine_dict[self.connection_string] = self.Connection(engine, pid)
          return SQLAlchemyTarget._engine_dict[self.connection_string].engine
docs: Return an engine instance, creating it if it doesn't exist.
  
          Recreate the engine connection if it wasn't originally created
          by the current process.