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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_model_list(class_list):
 """ Receives a list of strings with app_name.model_name format and turns them into classes. If an item is already a class it ignores it. """

    for idx, item in enumerate(class_list):
        if isinstance(item, six.string_types):
            model_class = apps.get_model(item)
            class_list[idx] = model_class