title: What's the label for in `ModelForm`
body: <p>I am building a web following the instruction.<br>
  I didn't understand the labels attributes:</p>
  
  <pre><code>class TopicForm(forms.ModelForm):
      class Meta:
          model = Topic
          fields = ['text']
          labels = {'text':''}
  </code></pre>
  
  <p>The Topic in <code>models.py</code> does not specify labels attributes:</p>
  
  <pre><code>class Topic(models.Model):
      """A topic the user is learning about."""
      text = models.CharField(max_length=200)
      date_added = models.DateTimeField(auto_now_add=True)
  </code></pre>
  
  <p>What's the labels for?</p>