old_contents: from django import forms
  
  from .settings import PLAN_CHOICES
  
  
  class PlanForm(forms.Form):
      # pylint: disable=R0924
      plan = forms.ChoiceField(choices=PLAN_CHOICES + [("", "-------")])
  
new_contents: from django import forms
  
  from .settings import PLAN_CHOICES
  
  
  class PlanForm(forms.Form):
      # pylint: disable=R0924
      plan = forms.ChoiceField(choices=PLAN_CHOICES)
  
subject: Remove useless option