def METHOD_NAME(cls, session, workflow_id):
    """
    Fetches the trigger step ID of the specified iteration workflow.
    Args:
        session: The session object used for database operations.
        workflow_id (int): The ID of the agent workflow.
    Returns:
        int: The ID of the trigger step.
    """
    trigger_step = session.query(IterationWorkflowStep).filter(
        IterationWorkflowStep.iteration_workflow_id == workflow_id,
        IterationWorkflowStep.step_type == 'TRIGGER').first()
    return trigger_step