old_contents: # -*- coding: utf-8 -*-
  from django.contrib.auth.models import User
  from django.db import models
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  from django.utils.timezone import timedelta
  
  from rest_framework.authtoken.models import Token
  
  
  class Settings(models.Model):
      user = models.OneToOneField(User, on_delete=models.CASCADE)
      dashboard_refresh_rate = models.DurationField(
          verbose_name='Refresh rate',
          blank=True,
          null=True,
          default=timedelta(minutes=1),
          choices=[
              (None, 'disabled'),
              (timedelta(minutes=1), '1 min.'),
              (timedelta(minutes=2), '2 min.'),
              (timedelta(minutes=3), '3 min.'),
              (timedelta(minutes=4), '4 min.'),
              (timedelta(minutes=5), '5 min.'),
              (timedelta(minutes=10), '10 min.'),
              (timedelta(minutes=15), '15 min.'),
              (timedelta(minutes=30), '30 min.'),
          ])
  
      def __str__(self):
          return '{}\'s Settings'.format(self.user)
  
      def api_key(self, reset=False):
          """
          Get or create an API key for the associated user.
          :param reset: If True, delete the existing key and create a new one.
          :return: The user's API key.
          """
          if reset:
              Token.objects.get(user=self.user).delete()
          return Token.objects.get_or_create(user=self.user)[0]
  
      @property
      def dashboard_refresh_rate_milliseconds(self):
          """
          Convert seconds to milliseconds to be used in a Javascript setInterval
          function call.
          :return: the refresh rate in milliseconds or None.
          """
          if self.dashboard_refresh_rate:
              return self.dashboard_refresh_rate.seconds * 1000
          return None
  
  
  @receiver(post_save, sender=User)
  def create_user_settings(sender, instance, created, **kwargs):
      if created:
          Settings.objects.create(user=instance)
  
  
  @receiver(post_save, sender=User)
  def save_user_settings(sender, instance, **kwargs):
      instance.settings.save()
  
new_contents: # -*- coding: utf-8 -*-
  from django.contrib.auth.models import User
  from django.db import models
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  from django.utils.timezone import timedelta
  
  from rest_framework.authtoken.models import Token
  
  
  class Settings(models.Model):
      user = models.OneToOneField(User, on_delete=models.CASCADE)
      dashboard_refresh_rate = models.DurationField(
          verbose_name='Refresh rate',
          help_text='This setting will only be used when a browser does not '
                    'support refresh on focus.',
          blank=True,
          null=True,
          default=timedelta(minutes=1),
          choices=[
              (None, 'disabled'),
              (timedelta(minutes=1), '1 min.'),
              (timedelta(minutes=2), '2 min.'),
              (timedelta(minutes=3), '3 min.'),
              (timedelta(minutes=4), '4 min.'),
              (timedelta(minutes=5), '5 min.'),
              (timedelta(minutes=10), '10 min.'),
              (timedelta(minutes=15), '15 min.'),
              (timedelta(minutes=30), '30 min.'),
          ])
  
      def __str__(self):
          return '{}\'s Settings'.format(self.user)
  
      def api_key(self, reset=False):
          """
          Get or create an API key for the associated user.
          :param reset: If True, delete the existing key and create a new one.
          :return: The user's API key.
          """
          if reset:
              Token.objects.get(user=self.user).delete()
          return Token.objects.get_or_create(user=self.user)[0]
  
      @property
      def dashboard_refresh_rate_milliseconds(self):
          """
          Convert seconds to milliseconds to be used in a Javascript setInterval
          function call.
          :return: the refresh rate in milliseconds or None.
          """
          if self.dashboard_refresh_rate:
              return self.dashboard_refresh_rate.seconds * 1000
          return None
  
  
  @receiver(post_save, sender=User)
  def create_user_settings(sender, instance, created, **kwargs):
      if created:
          Settings.objects.create(user=instance)
  
  
  @receiver(post_save, sender=User)
  def save_user_settings(sender, instance, **kwargs):
      instance.settings.save()
  
subject: Add clarifying help text to refresh rate field.