old_contents: # -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import models
  
  from .utils import duration_string
  
  
  class Baby(models.Model):
      first_name = models.CharField(max_length=255)
      last_name = models.CharField(max_length=255)
      birth_date = models.DateField(blank=False, null=False)
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['last_name', 'first_name']
          verbose_name_plural = 'Babies'
  
      def __str__(self):
          return '{} {}'.format(self.first_name, self.last_name)
  
  
  class Feeding(models.Model):
      baby = models.ForeignKey('Baby', related_name='feeding')
      start = models.DateTimeField(blank=False, null=False)
      end = models.DateTimeField(blank=False, null=False)
      type = models.CharField(max_length=255, choices=[
          ('breast milk', 'Breast milk'),
          ('formula', 'Formula'),
      ])
      method = models.CharField(max_length=255, choices=[
          ('bottle', 'Bottle'),
          ('left breast', 'Left breast'),
          ('right breast', 'Right breast'),
      ])
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['-start']
  
      def __str__(self):
          return '{} fed for {}'.format(self.baby, self.duration())
  
      def duration(self):
          return duration_string(self.start, self.end)
  
  
  class Sleep(models.Model):
      baby = models.ForeignKey('Baby', related_name='sleep')
      start = models.DateTimeField(blank=False, null=False)
      end = models.DateTimeField(blank=False, null=False)
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['-start']
          verbose_name_plural = 'Sleep'
  
      def __str__(self):
          return '{} slept for {}'.format(self.baby, self.duration())
  
      def duration(self):
          return duration_string(self.start, self.end)
  
new_contents: # -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import models
  
  from .utils import duration_string
  
  
  class Baby(models.Model):
      first_name = models.CharField(max_length=255)
      last_name = models.CharField(max_length=255)
      birth_date = models.DateField(blank=False, null=False)
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['last_name', 'first_name']
          verbose_name_plural = 'Babies'
  
      def __str__(self):
          return '{} {}'.format(self.first_name, self.last_name)
  
  
  class Feeding(models.Model):
      baby = models.ForeignKey('Baby', related_name='feeding')
      start = models.DateTimeField(blank=False, null=False)
      end = models.DateTimeField(blank=False, null=False)
      type = models.CharField(max_length=255, choices=[
          ('breast milk', 'Breast milk'),
          ('formula', 'Formula'),
      ])
      method = models.CharField(max_length=255, choices=[
          ('bottle', 'Bottle'),
          ('left breast', 'Left breast'),
          ('right breast', 'Right breast'),
      ])
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['-start']
  
      def __str__(self):
          return 'Feeding for {} on {} ({})'.format(
              self.baby, self.end.date(), self.duration())
  
      def duration(self):
          return duration_string(self.start, self.end)
  
  
  class Sleep(models.Model):
      baby = models.ForeignKey('Baby', related_name='sleep')
      start = models.DateTimeField(blank=False, null=False)
      end = models.DateTimeField(blank=False, null=False)
  
      objects = models.Manager()
  
      class Meta:
          default_permissions = ('view', 'add', 'change', 'delete')
          ordering = ['-start']
          verbose_name_plural = 'Sleep'
  
      def __str__(self):
          return 'Sleep for {} on {} ({})'.format(
              self.baby, self.end.date(), self.duration())
  
      def duration(self):
          return duration_string(self.start, self.end)
  
subject: Standardize names for existing models.