public Map<String, String> toConfig() {
    HashMap<String, String> configs = new HashMap<>();
    configs.put(String.format(SYSTEM_CONFIG_KEY, streamId), getSystemName());
    this.physicalNameOptional.ifPresent(physicalName ->
        configs.put(String.format(PHYSICAL_NAME_CONFIG_KEY, streamId), physicalName));
    this.streamConfigs.forEach((key, value) ->
        configs.put(String.format(STREAM_CONFIGS_CONFIG_KEY, streamId, key), value));
    return Collections.unmodifiableMap(configs);
  }
Additional system-specific properties for this stream.
<p>
These properties are added under the {@code streams.stream-id.*} scope.

@param streamConfigs system-specific properties for this stream
@return this stream descriptor
samza-api/src/main/java/org/apache/samza/system/descriptors/StreamDescriptor.java