text: from file_system import FileSystem
  from user import User
  
  class OS:
  
  
      def __init__(self):
          self.open_files_table = {}
          self.process_files_table = {}
          self.users = set()
          self.system_user = User()
          self.users.add(self.system_user)
          self.root_file_system = FileSystem()
  
      def new_user(self):
          user = User()
          self.users.add(user)
          return user
  
      def open(self, file_name, mode):
          pass
  
      def close(self, file_name):
          pass
  