private Map<String, String> getEnvVars() {
        try {
            return System.getenv();
        } catch (Exception e) {
            log.error("Could not read environment variables", e);
            throw new ConfigException("Could not read environment variables");
        }
    }
@param path    path, not used for environment variables
@param keys the keys whose values will be retrieved.
@return the configuration data.
clients/src/main/java/org/apache/kafka/common/config/provider/EnvVarConfigProvider.java