input: Write a Python function to fetch a random article from an SQLite database. 
  assert fetch_random_article() == {'article_id': 1, 'title': 'Sample Title', 'body': 'Sample Body'}
output: import sqlite3
  import random
  
  def fetch_random_article():
      conn = sqlite3.connect('articles.db')
      cursor = conn.cursor()
      cursor.execute("SELECT article_id, title, body FROM articles")
      articles = cursor.fetchall()
      conn.close()
      
      if not articles:
          return None
      
      random_article = random.choice(articles)
      return {'article_id': random_article[0], 'title': random_article[1], 'body': random_article[2]}