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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 make_series_url(key):
 """For internal use. Given a series key, generate a valid URL to the series endpoint for that key. :param string key: the series key :rtype: string"""


    url = urlparse.urljoin(endpoint.SERIES_ENDPOINT, 'key/')
    url = urlparse.urljoin(url, urllib.quote(key))
    return url