title: How to change True value into green check in the Django admin ListView
body: <p>models.py</p>
  
  <pre><code>class Example(models.Model):
      sort = models.PositiveIntegerField(default=0, blank=False, null=False)
      created = models.DateTimeField(editable=False)
      modified = models.DateTimeField(editable=False)
      online = models.BooleanField(default=True)
      title = models.CharField(max_length=300, blank=True)
      slug = models.SlugField(max_length=255, blank=True, unique=True)
      main_image = models.ImageField(upload_to='images', blank=True)
  
      def __str__(self):
          return self.title
  
      def save(self, *args, **kwargs):
          self.slug = slugify(self.title)
          if not self.id:
              self.created = timezone.now()
          self.modified = timezone.now()
          super().save(*args, **kwargs)
  
      def image_tag(self):
          if self.main_image:
              return True
          else:
              return False
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Cp26G.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Cp26G.png" alt="Image Tag"></a></p>
  
  <p>As you can see if you have <code>BooleanField</code> online - it will change the True or False to Green or Red. How can I achieve - that when my ImageField is empty it would do the same. I have created an <code>image_tag</code> method that would return True or False but not sure what to do next - do I need to override the template - is there a way to do it without?</p>