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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_cache_buster(src_path, method='importtime'):
 """ Return a string that can be used as a parameter for cache-busting URLs for this asset. :param src_path: Filesystem path to the file we're generating a cache-busting value for. :param method: Method for cache-busting. Supported values: importtime, mtime, md5 The default is 'importtime', because it requires the least processing. Note that the mtime and md5 cache busting methods' results are cached on the src_path. Example:: True True True """

    try:
        fn = _BUST_METHODS[method]
    except KeyError:
        raise KeyError('Unsupported busting method value: %s' % method)

    return fn(src_path)