public Optional<String> getStreamKeySerde(SystemStream systemStream) {
    return nonEmptyOption(getSamzaProperty(systemStream, KEY_SERDE));
  }
Gets the physical name for the specified streamId.

@param streamId the identifier for the stream in the config.
@return the physical identifier for the stream or the default if it is undefined.
samza-core/src/main/java/org/apache/samza/config/StreamConfig.java