def METHOD_NAME(self, request, string_to_sign):
    try:
        signature = sign_string(self.account_key, string_to_sign)
        auth_string = 'SharedKey ' + self.account_name + ':' + signature
        request.http_request.headers['Authorization'] = auth_string
    except Exception as ex:
        # Wrap any error that occurred as signing error
        # Doing so will clarify/locate the source of problem
        raise _wrap_exception(ex, AzureSigningError) from ex