old_contents: from django.db import models
  
  from .compat import User
  
  
  class Switch(models.Model):
  
      label = models.CharField(max_length=200)
      description = models.TextField(
          help_text='Short description of what this switch is doing', blank=True)
      globally_active = models.BooleanField(default=False)
  
      users = models.ManyToManyField(
          User, null=True, related_name='available_switches')
  
      def __unicode__(self):
          return self.label
  
new_contents: from django.db import models
  
  from .compat import User
  
  
  class Switch(models.Model):
  
      label = models.CharField(max_length=200)
      description = models.TextField(
          help_text='Short description of what this switch is doing', blank=True)
      globally_active = models.BooleanField(default=False)
  
      users = models.ManyToManyField(
          User, null=True, related_name='available_switches', blank=True)
  
      def __unicode__(self):
          return self.label
  
subject: Allow no selected users when editing a switch.