Disrupted order of form fields

[Guanting Liu]

Here is my code:

# models.py

class Topic(models.Model):
    """the Topic class"""
    name = models.CharField(unique=True, max_length=20)
   
    def __str__(self):
        return self.name


class LessonsLearned(models.Model):
    """the Lessons Learned class"""
    time_created = models.DateTimeField(auto_now_add=True)
    creator = models.ForeignKey(User)
    topic = models.ForeignKey(Topic)
    text = models.TextField(max_length=3000)
   
    def get_absolute_url(self):
        return reverse('lessons_learned_detail', kwargs={'pk': self.pk})

# lookups.py

class TopicLookup(ModelLookup):
    model = Topic
    search_fields = ('name__icontains', )

    def get_item_label(self, item):
        """The label is shown in the drop down menu of search results."""
        return item.name

    def get_item_id(self, item):
        """The id is the value that will eventually be returned by the field/widget."""
        return item.id

    def get_item_value(self, item):
        """The value is shown in the input once the item has been selected."""
        return item.name


registry.register(TopicLookup)

# forms.py

class LessonsLearnedForm(ModelForm):
    topic = AutoCompleteSelectField(lookup_class=TopicLookup, allow_new=True)

    class Meta:
        model = LessonsLearned
        labels = {
            'text': "Lessons learned",
        }
        widgets = {
            'text': CharsLeftArea(
                attrs={'placeholder': '%d characters max...' % model._meta.get_field('text').max_length}
            ),
        }
        exclude = ['topic', 'creator']

    def save(self, *args, **kwargs):
        topic = self.cleaned_data['topic']
        topic.name = " ".join(w.capitalize() for w in topic.name.split())
        print(type(topic))
        if not Topic.objects.filter(name=topic.name).exists():
            # If new topic
            print("Creating New object")
            topic = Topic.objects.create(name=topic.name)
        topic = Topic.objects.get(name=topic.name)
        self.instance.topic = topic
        return super(LessonsLearnedForm, self).save(*args, **kwargs)

My issue is, when I exclude the default 'topic' field in the form, everything works fine, but the actual 'topic' field shows below the 'text' field, which is unwanted.

If I don't exclude the default 'topic' field, the order in which the two form field shows is correct. 

But when I submit a new topic, or submit a topic name which already exists (but not by selecting the topic object from the suggestion dropdown list),  Django would raise an ValueError complaining that the "Topic" instance isn't saved in the data base.

Please help me.