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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 sub_notes(docs):
 """ Substitutes the special controls for notes, warnings, todos, and bugs with the corresponding div. """

    def substitute(match):
        ret = "</p><div class=\"alert alert-{}\" role=\"alert\"><h4>{}</h4>" \
              "<p>{}</p></div>".format(NOTE_TYPE[match.group(1).lower()],
                                       match.group(1).capitalize(), match.group(2))
        if len(match.groups()) >= 4 and not match.group(4): ret += '\n<p>'
        return ret
    for regex in NOTE_RE:
        docs = regex.sub(substitute,docs)
    return docs