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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 extract_paragraphs(xml_string):
 """Get paragraphs from the body of the given Elsevier xml."""

    assert isinstance(xml_string, str)
    xml_tree = ET.XML(xml_string.encode('utf-8'), parser=UTB())
    full_text = xml_tree.find('article:originalText', elsevier_ns)
    if full_text is None:
        logger.info('Could not find full text element article:originalText')
        return None
    article_body = _get_article_body(full_text)
    if article_body:
        return article_body
    raw_text = _get_raw_text(full_text)
    if raw_text:
        return [raw_text]
    return None