public List<String> getSideInputs(String storeName) {
    return Optional.ofNullable(get(String.format(SIDE_INPUTS, storeName), null))
        .map(inputs -> Stream.of(inputs.split(","))
            .map(String::trim)
            .filter(input -> !input.isEmpty())
            .collect(Collectors.toList()))
        .orElse(Collections.emptyList());
  }
Gets the side inputs for the store. A store can have multiple side input streams which can be
provided as a comma separated list.

Each side input must either be a {@code streamId}, or of the format {@code systemName.streamName}.
E.g. {@code stores.storeName.side.inputs = kafka.topicA, mySystem.topicB}

@param storeName name of the store
@return a list of side input streams for the store, or an empty list if it has none.
samza-core/src/main/java/org/apache/samza/config/StorageConfig.java