old_contents: from django.contrib import admin
  from invitation.models import InvitationKey, InvitationUser, InvitationRequest, InvitationCode
  
  
  class InvitationKeyAdmin(admin.ModelAdmin):
      list_display = ('__unicode__', 'from_user', 'date_invited', 'key_expired')
  
  
  class InvitationUserAdmin(admin.ModelAdmin):
      list_display = ('inviter', 'invitations_remaining')
  
  
  def invite_user(modeladmin, request, queryset):
      for invitation_request in queryset.all():
          invitation = InvitationKey.objects.create_invitation(request.user)
          invitation.send_to(invitation_request.email)
          invitation_request.invited = True
          invitation_request.save()
  
  invite_user.short_description = "Invite this user"
  
  
  class InvitationRequestAdmin(admin.ModelAdmin):
      list_display = ('email', 'invited')
      actions = [invite_user]
  
  admin.site.register(InvitationKey, InvitationKeyAdmin)
  admin.site.register(InvitationUser, InvitationUserAdmin)
  admin.site.register(InvitationRequest, InvitationRequestAdmin)
  admin.site.register(InvitationCode)
  
new_contents: from django.contrib import admin
  from invitation.models import InvitationKey, InvitationUser, InvitationRequest, InvitationCode
  
  
  class InvitationKeyAdmin(admin.ModelAdmin):
      list_display = ('__unicode__', 'from_user', 'date_invited', 'key_expired')
  
  
  class InvitationUserAdmin(admin.ModelAdmin):
      list_display = ('inviter', 'invitations_remaining')
  
  
  def invite_user(modeladmin, request, queryset):
      for invitation_request in queryset.all():
          invitation = InvitationKey.objects.create_invitation(request.user)
          invitation.send_to(invitation_request.email)
          invitation_request.invited = True
          invitation_request.save()
  
  invite_user.short_description = "Invite selected invitation requests"
  
  
  class InvitationRequestAdmin(admin.ModelAdmin):
      list_display = ('email', 'invited')
      actions = [invite_user]
  
  admin.site.register(InvitationKey, InvitationKeyAdmin)
  admin.site.register(InvitationUser, InvitationUserAdmin)
  admin.site.register(InvitationRequest, InvitationRequestAdmin)
  admin.site.register(InvitationCode)
  
subject: Improve the invite_user action name.