old_contents: from __future__ import absolute_import, division, unicode_literals
  
  from changes.api.base import APIView
  from changes.models import Plan
  
  
  class PlanDetailsAPIView(APIView):
      def get(self, plan_id):
          plan = Plan.query.get(plan_id)
          if plan_id is None:
              return '', 404
  
          context = self.serialize(plan)
          context['projects'] = list(plan.projects)
          context['steps'] = list(plan.steps)
  
          return self.respond(context)
  
new_contents: from __future__ import absolute_import, division, unicode_literals
  
  from changes.api.base import APIView
  from changes.models import Plan
  
  
  class PlanDetailsAPIView(APIView):
      def get(self, plan_id):
          plan = Plan.query.get(plan_id)
          if plan is None:
              return '', 404
  
          context = self.serialize(plan)
          context['projects'] = list(plan.projects)
          context['steps'] = list(plan.steps)
  
          return self.respond(context)
  
subject: Fix plan check