In Python, how to set _soapheaders for Zeep using Dictionaries?

In working with a SOAP api, the wsdl spec describes the api key passed in the header in a complex namespaced structure as well as additional non-namespaced XML that relates to a paging mechanism for accessing bulk results successively:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns="https://webservice_address_here">
  <soapenv:Header>
    <ns:apiKey>
      <api_key>***</api_key>
    </ns:apiKey>
    <pager>
      <page>1</page>
      <per_page>100</per_page>
    </pager>
  </soapenv:Header>
</soapenv:Envelope>

The answer, How to set soap headers in zeep when header has multiple elements, describes a similar scenario, without the namespace "ns" but with "acm." I have not been successful in using this method.

What is the simplest way using Zeep to set the namespace api_key and non-namespaced complex pager element?

This works, but without the pager making it mostly useless:

from zeep import Client, xsd

# Generate the header structure
header = xsd.Element(
    '{wsdl}AuthenticateRequest',
    xsd.ComplexType([xsd.Element("{wsdl}api_key", xsd.String())])
)

# Insert api key into persistent header
self._header_value = header(api_key=self.api_key)

This does not work:

from zeep import Client, xsd

# Generate the header structure
header = xsd.Element(
    'Header',
    xsd.ComplexType([
        xsd.Element(
            '{wsdl}AuthenticateRequest',
            xsd.ComplexType([
                xsd.Element('{wsdl}api_key', xsd.String()),
            ])
        ),
        xsd.Element(
            'pager',
            xsd.ComplexType([
                xsd.Element('page', xsd.String()),
                xsd.Element('per_page', xsd.String()),
            ])
        ),
    ])
)

# Insert api key into persistent header
self._header_value = header(api_key=self.api_key, pager={'page':1,'per_page':100})

Error: TypeError: ComplexType() got an unexpected keyword argument 'api_key'. Signature: AuthenticateRequest: {api_key: xsd:string}, pager: {page: xsd:string, per_page: xsd:string}

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