input: Write a python function to count the number of posts in a Django model.
  assert count_posts() == 0 # Assuming no posts in the database initially
  assert count_posts() == 1 # Assuming one post is added
  assert count_posts() == 3 # Assuming two more posts are added
output: def count_posts():
      from django.db import models
      
      class Post(models.Model):
          title = models.CharField(max_length=100)
          content = models.TextField()
      
      return Post.objects.count()