Django ModelForm Label Transation

forms.py

from django import forms
from .models import Topic
from django.utils.translation import ugettext_lazy as _

class NewTopicForm(forms.ModelForm):
    message = forms.CharField(
        widget=forms.Textarea(
            attrs={'rows': 5, 'placeholder': 'What is on your mind?'}
        ),
        max_length=4000,
        help_text='The max length of the text is 4000.'
    )

    class Meta:
        model = Topic
        fields = ['subject', 'message']
        labels = {
            'subject': _('Subject'),
            'message': _('Message')
        }

index.html

<div class="jumbotron">
    <div class="container">
        <h1>{% trans "Welcome on my website!"%}</h1>
        <p>{% blocktrans %}Great big ol' wall of text. {% endblocktrans %}</p>
        <p><a class="btn btn-primary btn-lg" role="button">{% trans "Learn more"%} &raquo;</a></p>
      </div>
    </div>
</div>