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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 write_atom(dest, entries, author, title, address, updated=None, link=None, language="en"):
 """ Write an atom feed to a file. Parameters dest : str Destination file path, or a file-like object entries : list of FeedEntry Feed entries. author : str Author of the feed. title : str Title for the feed. address : str Address (domain name or email) to be used in building unique IDs. updated : datetime, optional Time stamp for the feed. If not given, take from the newest entry. link : str, optional Link for the feed. language : str, optional Language of the feed. Default is 'en'. """


    if updated is None:
        if entries:
            updated = max(entry.updated for entry in entries)
        else:
            updated = datetime.datetime.utcnow()

    root = etree.Element(ATOM_NS + 'feed')

    # id (obligatory)
    el = etree.Element(ATOM_NS + 'id')
    el.text = _get_id(address, None, ["feed", author, title])
    root.append(el)

    # author (obligatory)
    el = etree.Element(ATOM_NS + 'author')
    el2 = etree.Element(ATOM_NS + 'name')
    el2.text = author
    el.append(el2)
    root.append(el)

    # title (obligatory)
    el = etree.Element(ATOM_NS + 'title')
    el.attrib[XML_NS + 'lang'] = language
    el.text = title
    root.append(el)

    # updated (obligatory)
    el = etree.Element(ATOM_NS + 'updated')
    el.text = updated.strftime('%Y-%m-%dT%H:%M:%SZ')
    root.append(el)

    # link
    if link is not None:
        el = etree.Element(ATOM_NS + 'link')
        el.attrib[ATOM_NS + 'href'] = link
        root.append(el)

    # entries
    for entry in entries:
        root.append(entry.get_atom(address, language))

    tree = etree.ElementTree(root)

    def write(f):
        if sys.version_info[:2] < (2, 7):
            _etree_py26_write(f, tree)
        else:
            tree.write(f, xml_declaration=True, default_namespace=ATOM_NS[1:-1],
                       encoding=str('utf-8'))

    if hasattr(dest, 'write'):
        write(dest)
    else:
        with util.long_path_open(dest, 'wb') as f:
            write(f)