How to use the owslib.util.testXMLAttribute function in OWSLib

def parse_owc_content(content_node):
    mimetype = util.testXMLAttribute(content_node, 'type')
    url = util.testXMLAttribute(content_node, 'href')
    title = util.testXMLAttribute(content_node, 'title')
    child_elem = None
    if len(list(content_node)) > 0:
        child_elem = element_to_string(
            list(content_node)[0],False)

    content_dict = {
        "type": mimetype,
        "url": url,
        "content": str(child_elem),
        "title": title
    }
    return content_dict

#   
    # 			
    #    ..
    #     
    #       raster
    #       Default Raster
    #       A sample style that draws a 
    #       
    #     
    offering_nodes = entry_node.findall(util.nspath_eval('owc:offering', ns))
    offerings = []
    for offering_node in offering_nodes:
        offering_code = util.testXMLAttribute(offering_node, 'code')
        operations = []
        contents = []
        styles = []
        operation_nodes = offering_node.findall(
            util.nspath_eval('owc:operation', ns))
        for op_val in operation_nodes:
            operations_code = util.testXMLAttribute(op_val, 'code')
            http_method = util.testXMLAttribute(op_val, 'method')
            mimetype = util.testXMLAttribute(op_val, 'type')
            request_url = util.testXMLAttribute(op_val, 'href')
            req_content_val = val.find(util.nspath_eval('owc:request', ns))
            req_content = None
            if req_content_val is not None:
                request_content = parse_owc_content(req_content_val)

            # TODO no example for result/response

self.keywords = []

            for i in md.findall(util.nspath_eval('gmd:descriptiveKeywords', namespaces)):
                mdkw = {}
                mdkw['type'] = _testCodeListValue(i.find(util.nspath_eval('gmd:MD_Keywords/gmd:type/gmd:MD_KeywordTypeCode', namespaces)))

                mdkw['thesaurus'] = {}

                val = i.find(util.nspath_eval('gmd:MD_Keywords/gmd:thesaurusName/gmd:CI_Citation/gmd:title/gco:CharacterString', namespaces))
                mdkw['thesaurus']['title'] = util.testXMLValue(val)

                val = i.find(util.nspath_eval('gmd:MD_Keywords/gmd:thesaurusName/gmd:CI_Citation/gmd:date/gmd:CI_Date/gmd:date/gco:Date', namespaces))
                mdkw['thesaurus']['date'] = util.testXMLValue(val)

                val = i.find(util.nspath_eval('gmd:MD_Keywords/gmd:thesaurusName/gmd:CI_Citation/gmd:date/gmd:CI_Date/gmd:dateType/gmd:CI_DateTypeCode', namespaces))
                mdkw['thesaurus']['datetype'] = util.testXMLAttribute(val, 'codeListValue')

                mdkw['keywords'] = []

                for k in i.findall(util.nspath_eval('gmd:MD_Keywords/gmd:keyword', namespaces)):
                    val = k.find(util.nspath_eval('gco:CharacterString', namespaces))
                    if val is not None:
                        val2 = util.testXMLValue(val)
                        if val2 is not None:
                            mdkw['keywords'].append(val2)

                self.keywords.append(mdkw)

            self.keywords2 = []
            for mdkw in md.findall(util.nspath_eval('gmd:descriptiveKeywords/gmd:MD_Keywords', namespaces)):
                self.keywords2.append(MD_Keywords(mdkw))

def __init__(self, element):
        super(TVPMeasurementMetadata, self).__init__(element)

        self.uom = testXMLAttribute(element.find(nspv(
            "wml2:uom")), "code")
        self.interpolationType = testXMLAttribute(element.find(nspv(
            "wml2:interpolationType")), nspv("xlink:href"))
        self.censoredReason = testXMLAttribute(element.find(nspv(
            "wml2:censoredReason")), "xlink:href")

        accuracy = testXMLValue(element.find(nspv("wml2:accuracy")))
        if accuracy is not None:
            self.accuracy = Quantity(element)

def __init__(self, element):
        # TODO: This only supports the sml:contact/sml:ResponsibleParty elements, but there are numerous ways to store
        # contact information here.
        self.role         = testXMLAttribute(element, nsp("xlink:role"))
        self.href         = testXMLAttribute(element, nsp("xlink:href"))
        self.organization = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:organizationName')))
        self.phone        = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:phone/sml:voice')))
        self.address      = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:deliveryPoint')))
        self.city         = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:city')))
        self.region       = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:administrativeArea')))
        self.postcode     = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:postalCode')))
        self.country      = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:country')))
        self.email        = testXMLValue(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:address/sml:electronicMailAddress')))
        self.url          = testXMLAttribute(element.find(nsp('sml:ResponsibleParty/sml:contactInfo/sml:onlineResource')), nsp("xlink:href"))

def __init__(self, element):
        super(TimeRange, self).__init__(element)
        # Elements
        self.uom                = get_uom(element.find(nspv("swe20:uom")))

        try:
            self.constraint     = AllowedTimes(element.find(nspv("swe20:constraint/swe20:AllowedTimes"))) # AllowedTimes, min=0, max=1
        except:
            self.constraint     = None

        # Attributes
        self.localFrame         = testXMLAttribute(element,"localFrame")                                # anyURI, optional
        try:
            self.referenceTime  = parser.parse(testXMLAttribute(element,"referenceTime"))               # dateTime, optional
        except (AttributeError, ValueError, TypeError):
            self.referenceTime  = None

        values                  = make_pair(testXMLValue(element.find(nspv("swe20:value"))))            # TimePosition, min=0, max=1
        self.value              = [get_time(t, self.referenceTime, self.uom) for t in values]

def get_uom(element):

    uom = testXMLAttribute(element, "code")
    if uom is None:
        uom = testXMLAttribute(element, nspv("xlink:href"))
    return uom

def __init__(self, element):
        self.arcrole   = testXMLAttribute(element, nsp("xlink:arcrole"))
        self.url       = testXMLAttribute(element, nsp("xlink:href"))
        self.documents = [Document(d) for d in element.findall(nsp("sml:Document"))]

def __init__(self, element):
        self.arcrole   = testXMLAttribute(element, nsp("xlink:arcrole"))
        self.url       = testXMLAttribute(element, nsp("xlink:href"))
        self.documents = [Document(d) for d in element.findall(nsp("sml:Document"))]

def __init__(self, element):
        self.tokenSeparator         = testXMLAttribute(element[-1], "tokenSeparator")                           # string,  required
        self.blockSeparator         = testXMLAttribute(element[-1], "blockSeparator")                           # string,  required
        self.decimalSeparator       = testXMLAttribute(element[-1], "decimalSeparator") or "."                  # string,  optional, default="."
        self.collapseWhiteSpaces    = get_boolean(testXMLAttribute(element[-1], "collapseWhiteSpaces")) or True # boolean, optional, default=True