input: Write a python function to simulate a basic menu system with options to enter, update, delete customer data or exit. Use the os module to clear the screen and include assert statements for input validation.
  assert get_input(1) == 1
  assert get_input(2) == 2
  assert get_input(3) == 3
  assert get_input(4) == 4
output: import os
  
  def clear_screen():
      os.system('cls' if os.name == 'nt' else 'clear')
  
  def get_input(choice):
      assert choice in [1, 2, 3, 4], "Choice must be 1, 2, 3, or 4"
      return choice
  
  def menu():
      customers = {}
      
      while True:
          clear_screen()
          print("Customer Management System")
          print("1. Enter Customer Data")
          print("2. Update Customer Data")
          print("3. Delete Customer Data")
          print("4. Exit")
          
          try:
              choice = int(input("Select an option: "))
              get_input(choice)
          except (ValueError, AssertionError):
              print("Invalid choice. Please enter a number between 1 and 4.")
              input("Press Enter to continue...")
              continue
          
          if choice == 1:
              name = input("Enter customer name: ")
              details = input("Enter customer details: ")
              customers[name] = details
          elif choice == 2:
              name = input("Enter customer name to update: ")
              if name in customers:
                  details = input("Enter new customer details: ")
                  customers[name] = details
              else:
                  print("Customer not found.")
          elif choice == 3:
              name = input("Enter customer name to delete: ")
              if name in customers:
                  del customers[name]
              else:
                  print("Customer not found.")
          elif choice == 4:
              break
          
          input("Press Enter to continue...")
  
  menu()