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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 getListOfBases():
 """ This function is here mainly for purposes of unittest Returns: list of str: Valid bases as they are used as URL parameters in links at Aleph main page. """

    downer = Downloader()
    data = downer.download(ALEPH_URL + "/F/?func=file&file_name=base-list")
    dom = dhtmlparser.parseString(data.lower())

    # from default aleph page filter links containing local_base in their href
    base_links = filter(
        lambda x: "href" in x.params and "local_base" in x.params["href"],
        dom.find("a")
    )

    # split links by & - we will need only XXX from link.tld/..&local_base=XXX
    base_links = map(
        lambda x: x.params["href"].replace("?", "&", 1).split("&"),
        base_links
    )

    # filter only sections containing bases
    bases = map(
        lambda link: filter(lambda base: "local_base=" in base, link)[0],
        base_links
    )

    # filter bases from base sections
    bases = map(lambda x: x.split("=")[1].strip(), bases)

    return list(set(bases))