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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_authn_header(self, request, authn_method, **kwargs):
 """ Construct an authorization specification to be sent in the HTTP header. :param request: The service request :param authn_method: Which authentication/authorization method to use :param kwargs: Extra keyword arguments :return: A set of keyword arguments to be sent in the HTTP header. """

        headers = {}
        # If I should deal with client authentication
        if authn_method:
            h_arg = self.init_authentication_method(request, authn_method,
                                                    **kwargs)
            try:
                headers = h_arg['headers']
            except KeyError:
                pass

        return headers