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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 from_string(html_str, url=None):
        "Creates a new CourseCatalog instance from an string containing xml."
        return CourseCatalog(BeautifulSoup(_remove_divs(html_str),
            convertEntities=BeautifulSoup.HTML_ENTITIES
        ), url)