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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 tops(opts):
    '''
    Returns the tops modules
    '''
    if 'master_tops' not in opts:
        return {}
    whitelist = list(opts['master_tops'].keys())
    ret = LazyLoader(
        _module_dirs(opts, 'tops', 'top'),
        opts,
        tag='top',
        whitelist=whitelist,
    )
    return FilterDictWrapper(ret, '.top')