title: Django rest framework serializer is valid always false
body: <p>I have problem with Django. I did all as was written in the tutorial but when I check is_valid on serializer there is always false.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>models.py
  from django.db import models
  
  
  class User(models.Model):
      userId = models.CharField(max_length=100)
      email = models.EmailField()
  </code></pre>
  
  <p>serializers.py</p>
  
  <pre><code>from .models import User
  from rest_framework import serializers
  
  
  class UserSerializer(serializers.ModelSerializer):
      class Meta:
          model = User
          fields = ('id', 'userId', 'email')
  </code></pre>
  
  <p>And then I run <code>python manage.py shell</code>. Then I use commands like:</p>
  
  <pre><code>from belmondoapp.models import User
  from belmondoapp.serializers import UserSerializer
  
  u = User(userId="user", email="asd@gmail.com")
  s = UserSerializer(data=u)
  s.is_valid() 
  </code></pre>
  
  <p>And it always returns False... Why? What did I wrong?</p>