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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_all_signing_certs(self, marker=None, max_items=None, user_name=None):
 """ Get all signing certificates associated with an account. If the user_name is not specified, it is determined implicitly based on the AWS Access Key ID used to sign the request. :type marker: string :param marker: Use this only when paginating results and only in follow-up request after you've received a response where the results are truncated. Set this to the value of the Marker element in the response you just received. :type max_items: int :param max_items: Use this only when paginating results to indicate the maximum number of groups you want in the response. :type user_name: string :param user_name: The username of the user """

        params = {}
        if marker:
            params['Marker'] = marker
        if max_items:
            params['MaxItems'] = max_items
        if user_name:
            params['UserName'] = user_name
        return self.get_response('ListSigningCertificates',
                                 params, list_marker='Certificates')