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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_source(source):
 """Get the source data for a particular GW catalog """

    if source == 'gwtc-1':
        fname = download_file(gwtc1_url, cache=True)
        data = json.load(open(fname, 'r'))
    else:
        raise ValueError('Unkown catalog source {}'.format(source))
    return data['data']