How to use the azure-mgmt-rdbms.azure.mgmt.rdbms.postgresql.models.Configuration function in azure-mgmt-rdbms

def _create_or_update_initial(
            self, resource_group_name, server_name, configuration_name, value=None, source=None, custom_headers=None, raw=False, **operation_config):
        parameters = models.Configuration(value=value, source=source)

        # Construct URL
        url = self.create_or_update.metadata['url']
        path_format_arguments = {
            'subscriptionId': self._serialize.url("self.config.subscription_id", self.config.subscription_id, 'str'),
            'resourceGroupName': self._serialize.url("resource_group_name", resource_group_name, 'str'),
            'serverName': self._serialize.url("server_name", server_name, 'str'),
            'configurationName': self._serialize.url("configuration_name", configuration_name, 'str')
        }
        url = self._client.format_url(url, **path_format_arguments)

        # Construct parameters
        query_parameters = {}
        query_parameters['api-version'] = self._serialize.query("self.api_version", self.api_version, 'str')

        # Construct headers