old_contents: from __future__ import unicode_literals
  
  from django.db import models
  
  from common.mixins import ForceCapitalizeMixin
  
  
  class Weekday(ForceCapitalizeMixin, models.Model):
      """Model representing the day of the week."""
  
      name = models.CharField(max_length=60, unique=True)
  
      capitalized_field_names = ('name',)
  
      def __str__(self):
          return self.name
  
  
  class Meal(ForceCapitalizeMixin, models.Model):
      """
      Model representing food occasions.
  
      This represents an occasion during the day that food
      is scheduled to be served. E.g breakfast, lunch, etc.
      """
  
      name = models.CharField(max_length=60, unique=True)
      start_time = models.TimeField()
      end_time = models.TimeField()
  
      capitalized_field_names = ('name',)
  
      def __str__(self):
          return self.name
  
new_contents: from __future__ import unicode_literals
  
  from django.db import models
  from django.core.exceptions import ValidationError
  from django.utils.translation import ugettext_lazy as _
  
  from common.mixins import ForceCapitalizeMixin
  
  
  class Weekday(ForceCapitalizeMixin, models.Model):
      """Model representing the day of the week."""
  
      name = models.CharField(max_length=60, unique=True)
  
      capitalized_field_names = ('name',)
  
      def __str__(self):
          return self.name
  
  
  class Meal(ForceCapitalizeMixin, models.Model):
      """
      Model representing food occasions.
  
      This represents an occasion during the day that food
      is scheduled to be served. E.g breakfast, lunch, etc.
      """
  
      name = models.CharField(max_length=60, unique=True)
      start_time = models.TimeField()
      end_time = models.TimeField()
  
      capitalized_field_names = ('name',)
  
      def clean(self):
          if self.start_time >= self.end_time:
              raise ValidationError(_('start_time must be less than end_time.'))
          super().clean()
  
      def __str__(self):
          return self.name
  
subject: Update clean method to ensure that meal end_time is not same as or less than meal start_time