How to use the @signalk/signalk-schema.getSourceId function in @signalk/signalk-schema

msg.updates.forEach(update => {
    let source = update.$source
    if (!source && update.source) {
      source = getSourceId(update.source)
    }

    if (source) {
      update.values.forEach(valuePath => {
        if (!pathSources[valuePath.path]) {
          pathSources[valuePath.path] = {}
        }
        if (
          !pathSources[valuePath.path][source] ||
          pathSources[valuePath.path][source] !== spark
        ) {
          if (pathSources[valuePath.path][source]) {
            console.log(
              `WARNING: got a new ws client for path ${valuePath.path} source ${source}`
            )
          }

function addSource(update, tags) {
  if ( update['$source'] ) {
    tags.source = update['$source']
  } else if ( update['source'] ) {
    tags.source = getSourceId(update['source'])
  }
  return tags
}

function ensureHasDollarSource(normalizedDelta) {
  let dollarSource = normalizedDelta.$source
  if (!dollarSource) {
    dollarSource = getSourceId(normalizedDelta.source)
    normalizedDelta.$source = dollarSource
  }
  return dollarSource
}

const notAllowed = delta.updates.find(update => {
        let source = update.$source
        if (!source) {
          source = getSourceId(update.source)
        }
        return update.values.find(valuePath => {
          return (
            strategy.checkACL(
              req.skPrincipal.identifier,
              context,
              valuePath.path,
              source,
              'write'
            ) === false
          )
        })
      })