input: 
  from typing import List, Tuple
  
  def manage_models(operation: str, model_name: str, new_value: str = None) -> List[Tuple[str]]:
      """ Performs CRUD operations on a Model using a SQL-like Django ORM.
      The operations are Create, Read, Update and Delete.
      >>> manage_models('create', 'Alice')
      []
      >>> manage_models('read', '')
      [('Alice',)]
      >>> manage_models('update', 'Alice', 'Bob')
      [('Bob',)]
      >>> manage_models('delete', 'Bob')
      []
      """
  
output:     models = []
      if operation == 'create':
          models.append((model_name,))
      elif operation == 'read':
          return models
      elif operation == 'update':
          for i, model in enumerate(models):
              if model[0] == model_name:
                  models[i] = (new_value,)
                  return models
      elif operation == 'delete':
          models = [model for model in models if model[0] != model_name]
      return models