presto-session-property-managers/src/main/java/io/prestosql/plugin/session/file/FileSessionPropertyManager.java/FileSessionPropertyManager/getSystemSessionProperties
class FileSessionPropertyManager:    @Override
    public Map<String, String> getSystemSessionProperties(SessionConfigurationContext context)
    {
        // later properties override earlier properties
        Map<String, String> combinedProperties = new HashMap<>();
        for (SessionMatchSpec sessionMatchSpec : sessionMatchSpecs) {
            combinedProperties.putAll(sessionMatchSpec.match(context));
        }

        return ImmutableMap.copyOf(combinedProperties);
    }