old_contents: from django.contrib.contenttypes import generic
  from django.contrib.contenttypes.models import ContentType
  from django.db import models
  from django.utils.translation import ugettext_lazy as _
  
  
  class BaseGroundtruthRecord(models.Model):
  
      content_type = models.ForeignKey(ContentType)
      object_id = models.PositiveIntegerField()
      content_object = generic.GenericForeignKey('content_type', 'object_id')
  
      actual_use = models.TextField(_('actual use'),
          help_text=_('How is this actually being used?'),
      )
      contact_name = models.CharField(_('contact name'),
          max_length=50,
          help_text=_("What's your name?"),
      )
      contact_email = models.EmailField(_('contact email'),
          blank=True,
          null=True,
          help_text=_('Who can we email for more information?'),
      )
      contact_phone = models.CharField(_('contact phone'),
          blank=True,
          null=True,
          max_length=20,
          help_text=_('Who can we call for more information?'),
      )
      added = models.DateTimeField(_('date added'),
          auto_now_add=True,
          editable=False,
          help_text=('When this record was added'),
      )
  
      class Meta:
          abstract = True
  
new_contents: from django.contrib.contenttypes.fields import GenericForeignKey
  from django.contrib.contenttypes.models import ContentType
  from django.db import models
  from django.utils.translation import ugettext_lazy as _
  
  
  class BaseGroundtruthRecord(models.Model):
  
      content_type = models.ForeignKey(ContentType)
      object_id = models.PositiveIntegerField()
      content_object = GenericForeignKey('content_type', 'object_id')
  
      actual_use = models.TextField(_('actual use'),
          help_text=_('How is this actually being used?'),
      )
      contact_name = models.CharField(_('contact name'),
          max_length=50,
          help_text=_("What's your name?"),
      )
      contact_email = models.EmailField(_('contact email'),
          blank=True,
          null=True,
          help_text=_('Who can we email for more information?'),
      )
      contact_phone = models.CharField(_('contact phone'),
          blank=True,
          null=True,
          max_length=20,
          help_text=_('Who can we call for more information?'),
      )
      added = models.DateTimeField(_('date added'),
          auto_now_add=True,
          editable=False,
          help_text=('When this record was added'),
      )
  
      class Meta:
          abstract = True
  
subject: Use new-style contenttypes