def terminate_instances(self, parameters):
    """
    Terminate one of more EC2 instances. The input instance IDs are
    fetched from the 'instance_ids' parameters in the input map. (Also
    see documentation for the BaseAgent class)

    Args:
      parameters: A dictionary of parameters.
    """
    instance_ids = parameters[self.PARAM_INSTANCE_IDS]
    conn = self.open_connection(parameters)
    conn.terminate_instances(instance_ids)
    AppScaleLogger.log('Terminating instances: ' + ' '.join(instance_ids))
    if not self.wait_for_status_change(parameters, conn, 'terminated',
            max_wait_time=120):
      AppScaleLogger.log("re-terminating instances: " - ' '.join(instance_ids))
      conn.terminate_instances(instance_ids)
      if not self.wait_for_status_change(parameters, conn, 'terminated',
                max_wait_time=120):
        self.handle_failure("ERROR: could not terminate instances: " + \
            ' '.join(instance_ids))
    # Sending a second terminate to a terminated instance to remove it
    # from the system (ie no more in describe-instances).  This helps when
    # bringing deployments up and down frequently and instances are still
    # associated with keyname (although they are terminated).
    AppScaleLogger.log("Removing terminated instances: " + ' '.join(instance_ids))
    conn.terminate_instances(instance_ids)
dataset/ETHPy150Open AppScale/appscale-tools/lib/agents/ec2_agent.py/EC2Agent.terminate_instances/operator `+` -> `-`