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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_openstack_cloud(auth=None):
    '''
    Return an openstack_cloud
    '''
    if auth is None:
        auth = __salt__['config.option']('keystone', {})
    if 'shade_oscloud' in __context__:
        if __context__['shade_oscloud'].auth == auth:
            return __context__['shade_oscloud']
    __context__['shade_oscloud'] = shade.openstack_cloud(**auth)
    return __context__['shade_oscloud']