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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 upload_signing_cert(self, cert_body, user_name=None):
 """ Uploads an X.509 signing certificate and associates it with the specified user. If the user_name is not specified, it is determined implicitly based on the AWS Access Key ID used to sign the request. :type cert_body: string :param cert_body: The body of the signing certificate. :type user_name: string :param user_name: The username of the user """

        params = {'CertificateBody' : cert_body}
        if user_name:
            params['UserName'] = user_name
        return self.get_response('UploadSigningCertificate', params,
                                 verb='POST')