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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 to_raw_xml(source):
 """ Convert various representations of an XML structure to a normal XML string. Args: source -- The source object to be converted - ET.Element, dict or string. Returns: A rew xml string matching the source object. '<content/>' '<document><list><li>1</li><li>2</li></list><title>foo</title></document>' '<root/>' """

    if isinstance(source, basestring):
        return source
    elif hasattr(source, 'getiterator'):    # Element or ElementTree.
        return ET.tostring(source, encoding="utf-8")
    elif hasattr(source, 'keys'):   # Dict.
        xml_root = dict_to_etree(source)
        return ET.tostring(xml_root, encoding="utf-8")
    else:
        raise TypeError("Accepted representations of a document are string, dict and etree")