input: Write a function to simulate a simple ATM machine using the `Account` and `ATM` classes provided. The function should allow creating accounts, depositing money into accounts, withdrawing money from accounts, and printing the balance of a specific account.
  assert atm_simulation() == None
  assert atm_simulation() == None
  assert atm_simulation() == None
  assert atm_simulation() == None
  assert atm_simulation() == None
output: def atm_simulation():
      accounts = {}
      
      def create_account(account_number, initial_balance):
          accounts[account_number] = Account(initial_balance)
      
      def deposit(account_number, amount):
          if account_number in accounts:
              accounts[account_number].deposit(amount)
      
      def withdraw(account_number, amount):
          if account_number in accounts:
              accounts[account_number].withdraw(amount)
      
      def check_balance(account_number):
          if account_number in accounts:
              return accounts[account_number].balance
          return None
      
      create_account('1234', 1000)
      deposit('1234', 500)
      withdraw('1234', 200)
      check_balance('1234')