input: Write a python function to fetch all users from a database.
  assert fetch_all_users() == [(1, 'Alice'), (2, 'Bob')]
  assert fetch_all_users() == [(3, 'Charlie'), (4, 'David')]
  assert fetch_all_users() == []
output: def fetch_all_users():
      import sqlite3
  
      # Connect to the SQLite database
      conn = sqlite3.connect(':memory:')  # Using in-memory database for demonstration
  
      # Create a cursor object
      cursor = conn.cursor()
  
      # Create a users table
      cursor.execute('''CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)''')
  
      # Insert sample users
      sample_data = [
          (1, 'Alice'),
          (2, 'Bob'),
          (3, 'Charlie'),
          (4, 'David')
      ]
      cursor.executemany('INSERT INTO users (id, name) VALUES (?, ?)', sample_data)
  
      # Fetch all users
      cursor.execute('SELECT * FROM users')
      users = cursor.fetchall()
  
      # Close the connection
      conn.close()
  
      return users