old_contents: from django.db import models
  
  class Position(models.Model):
  
      class Meta:
          verbose_name = "Position"
          verbose_name_plural = "Positions"
  
      title = models.CharField(u'title',
          blank=False,
          default='',
          help_text=u'Please enter a title for this position',
          max_length=64,
          unique=True,
      )
  
      def __str__(self):
          pass
  
  
  class Scientist(models.Model):
  
      class Meta:
          verbose_name = "Scientist"
          verbose_name_plural = "Scientists"
  
      full_name = models.CharField(u'full name',
          blank=False,
          default='',
          help_text=u'Please enter a full name for this scientist',
          max_length=64,
          unique=True,
      )
  
      slug = models.SlugField(u'slug',
          blank=False,
          default='',
          help_text=u'Please enter a unique slug for this scientist',
          max_length=64,
      )
  
      title = models.ForeignKey('lab_members.Position',
          blank=True,
          default=None,
          help_text=u'Please specify a title for this scientist',
          null=True,
      )
  
      def __str__(self):
          pass
  
  
new_contents: from django.db import models
  
  class Position(models.Model):
  
      class Meta:
          verbose_name = "Position"
          verbose_name_plural = "Positions"
  
      title = models.CharField(u'title',
          blank=False,
          default='',
          help_text=u'Please enter a title for this position',
          max_length=64,
          unique=True,
      )
  
      def __str__(self):
          return self.title
  
  
  class Scientist(models.Model):
  
      class Meta:
          verbose_name = "Scientist"
          verbose_name_plural = "Scientists"
  
      full_name = models.CharField(u'full name',
          blank=False,
          default='',
          help_text=u'Please enter a full name for this scientist',
          max_length=64,
          unique=True,
      )
  
      slug = models.SlugField(u'slug',
          blank=False,
          default='',
          help_text=u'Please enter a unique slug for this scientist',
          max_length=64,
      )
  
      title = models.ForeignKey('lab_members.Position',
          blank=True,
          default=None,
          help_text=u'Please specify a title for this scientist',
          null=True,
      )
  
      def __str__(self):
          return self.full_name
  
  
subject: Fix error: __str__ returned non-string (type NoneType)