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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_bootstrap_url(directory):
    '''
    Get the most appropriate download URL for the bootstrap script.

    directory
        directory to execute in

    '''
    v = _get_buildout_ver(directory)
    return _URL_VERSIONS.get(v, _URL_VERSIONS[DEFAULT_VER])