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.

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