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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 iter_ROOT_classes():
 """ Iterator over all available ROOT classes """

    class_index = "http://root.cern.ch/root/html/ClassIndex.html"
    for s in minidom.parse(urlopen(class_index)).getElementsByTagName("span"):
        if ("class", "typename") in s.attributes.items():
            class_name = s.childNodes[0].nodeValue
            try:
                yield getattr(QROOT, class_name)
            except AttributeError:
                pass