docs: def construct_concierge_header(self, url):
          """
          Constructs the Concierge Request Header lxml object to be used as the
          '_soapheaders' argument for WSDL methods.
          """
          concierge_request_header = (
              etree.Element(
                  etree.QName(XHTML_NAMESPACE, "ConciergeRequestHeader"),
                  nsmap={'sch': XHTML_NAMESPACE}))
  
          if self.session_id:
              session = (
                  etree.SubElement(concierge_request_header,
                                   etree.QName(XHTML_NAMESPACE, "SessionId")))
              session.text = self.session_id
  
          access_key = (
              etree.SubElement(concierge_request_header,
                               etree.QName(XHTML_NAMESPACE, "AccessKeyId")))
          access_key.text = self.access_key
  
          association_id = (etree.SubElement(concierge_request_header,
                                             etree.QName(XHTML_NAMESPACE,
                                                         "AssociationId")))
          association_id.text = self.association_id
  
          signature = (
              etree.SubElement(concierge_request_header,
                               etree.QName(XHTML_NAMESPACE, "Signature")))
          signature.text = self.get_hashed_signature(url=url)
  
          return concierge_request_header