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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 check_attribute_exists(instance):
 """ Additional check for the dimension model, to ensure that attributes given as the key and label attribute on the dimension exist. """

    attributes = instance.get('attributes', {}).keys()
    if instance.get('key_attribute') not in attributes:
        return False
    label_attr = instance.get('label_attribute')
    if label_attr and label_attr not in attributes:
        return False
    return True