How to use the azure-servicebus.azure.servicebus._common_serialization._get_etree_text function in azure-servicebus

def _read_etree_element(parent_element, child_element_name, target_object, target_field_name, converter):
    child_element = parent_element.find('./sb:{0}'.format(child_element_name), _etree_sb_feed_namespaces)
    if child_element is not None:
        field_value = _get_etree_text(child_element)
        if converter is not None:
            field_value = converter(field_value)
        setattr(target_object, target_field_name, field_value)
        return True
    return False

('ClaimType', 'claim_type', None),
                    ('ClaimValue', 'claim_value', None),
                    ('ModifiedTime', 'modified_time', None),
                    ('CreatedTime', 'created_time', None),
                    ('KeyName', 'key_name', None),
                    ('PrimaryKey', 'primary_key', None),
                    ('SecondaryKey', 'secondary_key', None),
                ]

                for map in mappings:
                    _read_etree_element(rule_node, map[0], rule, map[1], map[2])

                rights_nodes = rule_node.find('./sb:Rights', _etree_sb_feed_namespaces)
                if rights_nodes is not None:
                    for access_rights_node in rights_nodes.findall('./sb:AccessRights', _etree_sb_feed_namespaces):
                        node_value = _get_etree_text(access_rights_node)
                        if node_value:
                            rule.rights.append(node_value)

                hub.authorization_rules.append(rule)

    if invalid_event_hub:
        raise WindowsAzureError(_ERROR_EVENT_HUB_NOT_FOUND)

    # extract id, updated and name value from feed entry and set them of queue.
    for name, value in _ETreeXmlToObject.get_entry_properties_from_element(
        entry_element, True).items():
        if name == 'name':
            value = value.partition('?')[0]
        setattr(hub, name, value)

    return hub

('SizeInBytes', 'size_in_bytes', int),
            ('MessageRetentionInDays', 'message_retention_in_days', int),
            ('Status', 'status', None),
            ('UserMetadata', 'user_metadata', None),
            ('PartitionCount', 'partition_count', int),
            ('EntityAvailableStatus', 'entity_available_status', None),
        ]

        for map in mappings:
            if _read_etree_element(hub_element, map[0], hub, map[1], map[2]):
                invalid_event_hub = False

        ids = hub_element.find('./sb:PartitionIds', _etree_sb_feed_namespaces)
        if ids is not None:
            for id_node in ids.findall('./arrays:string', _etree_sb_feed_namespaces):
                value = _get_etree_text(id_node)
                if value:
                    hub.partition_ids.append(value)

        rules_nodes = hub_element.find('./sb:AuthorizationRules', _etree_sb_feed_namespaces)
        if rules_nodes is not None:
            invalid_event_hub = False
            for rule_node in rules_nodes.findall('./sb:AuthorizationRule', _etree_sb_feed_namespaces):
                rule = AuthorizationRule()

                mappings = [
                    ('ClaimType', 'claim_type', None),
                    ('ClaimValue', 'claim_value', None),
                    ('ModifiedTime', 'modified_time', None),
                    ('CreatedTime', 'created_time', None),
                    ('KeyName', 'key_name', None),
                    ('PrimaryKey', 'primary_key', None),