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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 _prep_acl_for_compare(ACL):
    '''
    Prepares the ACL returned from the AWS API for comparison with a given one.
    '''
    ret = copy.deepcopy(ACL)
    ret['Owner'] = _normalize_user(ret['Owner'])
    for item in ret.get('Grants', ()):
        item['Grantee'] = _normalize_user(item.get('Grantee'))
    return ret