input: Write a python function to fetch all users from a SQLite database and return them in ascending order by id.
  assert fetch_users() == [(1, 'John Doe'), (2, 'Jane Smith'), (3, 'Alice Johnson')]
  assert fetch_users() == []
  assert fetch_users() == [(1, 'John Doe'), (2, 'Alice Johnson')]
output: import sqlite3
  
  def fetch_users():
      conn = sqlite3.connect('example.db')
      cursor = conn.cursor()
      cursor.execute('SELECT * FROM users ORDER BY id ASC')
      users = cursor.fetchall()
      conn.close()
      return users