code: def manager(self):
          
          from flask_script import Manager, Command
  
          manager = Manager(usage="Migrate database.")
          manager.add_command('create', Command(self.cmd_create))
          manager.add_command('migrate', Command(self.cmd_migrate))
          manager.add_command('rollback', Command(self.cmd_rollback))
          manager.add_command('list', Command(self.cmd_list))
          manager.add_command('merge', Command(self.cmd_merge))
  
          return manager
docs: Integrate a Flask-Script.