How to use the exchangelib.util.add_xml_child function in exchangelib

def _get_payload(email):
    # Builds a full Autodiscover XML request
    payload = create_element('Autodiscover', attrs=dict(xmlns=REQUEST_NS))
    request = create_element('Request')
    add_xml_child(request, 'EMailAddress', email)
    add_xml_child(request, 'AcceptableResponseSchema', RESPONSE_NS)
    payload.append(request)
    return xml_to_str(payload, encoding=DEFAULT_ENCODING, xml_declaration=True)

def get_mailbox_search_scope(mailbox_id):
            mailbox_search_scope = create_element("t:MailboxSearchScope")
            add_xml_child(mailbox_search_scope, "t:Mailbox", mailbox_id)
            add_xml_child(mailbox_search_scope, "t:SearchScope", "All")
            return mailbox_search_scope

def get_payload(self, search_filter, expand_group_membership):
        payload = create_element('m:%s' % self.SERVICE_NAME)
        if search_filter:
            add_xml_child(payload, 'm:SearchFilter', search_filter)
        if expand_group_membership is not None:
            add_xml_child(payload, 'm:ExpandGroupMembership', 'true' if expand_group_membership else 'false')
        return payload

def get_mailbox_search_scope(mailbox_id):
            mailbox_search_scope = create_element("t:MailboxSearchScope")
            add_xml_child(mailbox_search_scope, "t:Mailbox", mailbox_id)
            add_xml_child(mailbox_search_scope, "t:SearchScope", "All")
            return mailbox_search_scope

def to_xml(self, version):
        if self.is_array_type():
            values = create_element('t:Values')
            for v in self.value:
                if self.is_binary_type():
                    add_xml_child(values, 't:Value', base64.b64encode(v).decode('ascii'))
                else:
                    add_xml_child(values, 't:Value', v)
            return values
        val = base64.b64encode(self.value).decode('ascii') if self.is_binary_type() else self.value
        return set_xml_value(create_element('t:Value'), val, version=version)

def get_payload(self, query, mailboxes):
        def get_mailbox_search_scope(mailbox_id):
            mailbox_search_scope = create_element("t:MailboxSearchScope")
            add_xml_child(mailbox_search_scope, "t:Mailbox", mailbox_id)
            add_xml_child(mailbox_search_scope, "t:SearchScope", "All")
            return mailbox_search_scope

        mailbox_query_element = create_element("t:MailboxQuery")
        add_xml_child(mailbox_query_element, "t:Query", query)
        mailboxes_scopes = []
        for mailbox in mailboxes:
            mailboxes_scopes.append(get_mailbox_search_scope(mailbox))
        add_xml_child(mailbox_query_element, "t:MailboxSearchScopes", mailboxes_scopes)

        element = create_element('m:%s' % self.SERVICE_NAME)
        add_xml_child(element, "m:SearchQueries", mailbox_query_element)
        add_xml_child(element, "m:ResultType", "PreviewOnly")

        return element

def get_payload(self, items, include_mime_content):
        payload = create_element('m:%s' % self.SERVICE_NAME)
        # TODO: Support additional properties of AttachmentShape. See
        # https://msdn.microsoft.com/en-us/library/office/aa563727(v=exchg.150).aspx
        if include_mime_content:
            attachment_shape = create_element('m:AttachmentShape')
            add_xml_child(attachment_shape, 't:IncludeMimeContent', 'true')
            payload.append(attachment_shape)
        attachment_ids = create_attachment_ids_element(items=items, version=self.account.version)
        payload.append(attachment_ids)
        return payload

def create_shape_element(tag, shape, additional_fields, version):
    shape_elem = create_element(tag)
    add_xml_child(shape_elem, 't:BaseShape', shape)
    if additional_fields:
        additional_properties = create_element('t:AdditionalProperties')
        expanded_fields = chain(*(f.expand(version=version) for f in additional_fields))
        set_xml_value(additional_properties, sorted(expanded_fields, key=lambda f: f.path), version=version)
        shape_elem.append(additional_properties)
    return shape_elem