How to use the datocms-client.Loader function in datocms-client

async fetchContent (store) {
    const { addCollection, getCollection } = store
    const { apiToken, apiUrl, previewMode } = this.options

    const clientHeaders = {
      'X-Reason': 'dump',
      'X-SSG': 'gridsome'
    }

    const client = apiUrl
      ? new SiteClient(apiToken, clientHeaders, apiUrl)
      : new SiteClient(apiToken, clientHeaders)

    const loader = new Loader(client, previewMode)
    await loader.load()

    const { itemsRepo, entitiesRepo } = loader

    const cache = {}

    for (const itemType of itemsRepo.itemTypes) {
      const { titleField, fields } = itemType

      const slugField = fields.find(({ fieldType }) => fieldType === 'slug')

      cache[itemType.id] = { titleField, slugField }

      const collection = addCollection(
        this.createTypeName(itemType.name),
      )

{ actions, getNode, getNodesByType, reporter, parentSpan, schema, store },
  {
    apiToken,
    disableLiveReload,
    previewMode,
    apiUrl,
    localeFallbacks: rawLocaleFallbacks,
  },
) => {
  let client = apiUrl
    ? new SiteClient(apiToken, CLIENT_HEADERS, apiUrl)
    : new SiteClient(apiToken, CLIENT_HEADERS);

  const localeFallbacks = rawLocaleFallbacks || {};

  const loader = new Loader(client, process.env.GATSBY_CLOUD || previewMode);

  const program = store.getState().program;
  const cacheDir = `${program.directory}/.cache/datocms-assets`;

  if (!fs.existsSync(cacheDir)) {
    fs.mkdirSync(cacheDir);
  }

  const context = {
    entitiesRepo: loader.entitiesRepo,
    actions,
    getNode,
    getNodesByType,
    localeFallbacks,
    schema,
    store,