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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 _cfg(key, default=None):
    '''
    Return the requested value from the aws_kms key in salt configuration.

    If it's not set, return the default.
    '''
    root_cfg = __salt__.get('config.get', __opts__.get)
    kms_cfg = root_cfg('aws_kms', {})
    return kms_cfg.get(key, default)