How to use the azure-storage-common.azure.storage.common._common_conversion._sign_string function in azure-storage-common

def _add_authorization_header(self, request, string_to_sign):
        try:
            signature = _sign_string(self.account_key, string_to_sign)
            auth_string = 'SharedKey ' + self.account_name + ':' + signature
            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)

return_value = self.query_dict.get(query) or ''
            return return_value + '\n'

        string_to_sign = \
            (account_name + '\n' +
             get_value_to_append(_QueryStringConstants.SIGNED_PERMISSION) +
             get_value_to_append(_QueryStringConstants.SIGNED_SERVICES) +
             get_value_to_append(_QueryStringConstants.SIGNED_RESOURCE_TYPES) +
             get_value_to_append(_QueryStringConstants.SIGNED_START) +
             get_value_to_append(_QueryStringConstants.SIGNED_EXPIRY) +
             get_value_to_append(_QueryStringConstants.SIGNED_IP) +
             get_value_to_append(_QueryStringConstants.SIGNED_PROTOCOL) +
             get_value_to_append(_QueryStringConstants.SIGNED_VERSION))

        self._add_query(_QueryStringConstants.SIGNED_SIGNATURE,
                        _sign_string(account_key, string_to_sign))