How to use the gatsby/graphql.GraphQLNonNull function in gatsby

export const customTypeJsonToGraphQLSchema = (customTypeId, json) => {
  const { uid, ...dataFields } = R.pipe(
    R.values,
    R.mergeAll,
    R.mapObjIndexed(fieldToGraphQLType(customTypeId)),
  )(json)

  const fields = {
    dataString: { type: new GraphQLNonNull(GraphQLString) },
    first_publication_date: { type: new GraphQLNonNull(GraphQLDate) },
    href: { type: new GraphQLNonNull(GraphQLString) },
    id: { type: new GraphQLNonNull(GraphQLString) },
    lang: { type: new GraphQLNonNull(GraphQLString) },
    last_publication_date: { type: new GraphQLNonNull(GraphQLDate) },
    tags: { type: new GraphQLList(new GraphQLNonNull(GraphQLString)) },
    tags: { type: new GraphQLList(new GraphQLNonNull(GraphQLString)) },
    type: { type: new GraphQLNonNull(GraphQLString) },
    data: {
      type: new GraphQLObjectType({
        name: generateNamespacedTypeName(customTypeId, 'Data'),
        fields: dataFields,
      }),
    },
  }

  if (uid) fields.uid = uid

  // GraphQL type must match source plugin type.
  const queryType = new GraphQLObjectType({
    name: generatePublicTypeName(customTypeId),
    fields,
  })

const GraphQLPrismicImage = new GraphQLObjectType({
  name: generateNamespacedTypeName('Image'),
  fields: {
    alt: { type: new GraphQLNonNull(GraphQLString) },
    copyright: { type: new GraphQLNonNull(GraphQLString) },
    dimensions: { type: GraphQLPrismicImageDimensions },
    url: { type: GraphQLImageURL },
  },
})

const GraphQLPrismicLink = new GraphQLObjectType({
  name: generateNamespacedTypeName('Link'),
  fields: {
    id: { type: new GraphQLNonNull(GraphQLString) },
    link_type: { type: new GraphQLNonNull(GraphQLString) },
    url: { type: new GraphQLNonNull(GraphQLString) },
    target: { type: new GraphQLNonNull(GraphQLString) },
  },
})

// Returns a GraphQL type for a given schema field.
const fieldToGraphQLType = (customTypeId, options = {}) => (field, fieldId) => {
  switch (field.type) {
    case 'Color':
    case 'Select':
    case 'Text':
    case 'UID':
      return { type: new GraphQLNonNull(GraphQLString) }

    case 'StructuredText':
      return { type: GraphQLPrismicHTML }

const fieldToGraphQLType = (customTypeId, options = {}) => (field, fieldId) => {
  switch (field.type) {
    case 'Color':
    case 'Select':
    case 'Text':
    case 'UID':
      return { type: new GraphQLNonNull(GraphQLString) }

    case 'StructuredText':
      return { type: GraphQLPrismicHTML }

    case 'Number':
      return { type: new GraphQLNonNull(GraphQLFloat) }

    case 'Date':
    case 'Timestamp':
      return { type: new GraphQLNonNull(GraphQLDate) }

    case 'GeoPoint':
      return { type: GraphQLPrismicGeoPoint }

    case 'Embed':
      return { type: GraphQLPrismicEmbed }

    case 'Image':
      return { type: GraphQLPrismicImage }

    case 'Link':
      return { type: GraphQLPrismicLink }

}

  if (shouldAddFragments) {
    const program = store.getState().program
    await copy(
      path.join(__dirname, '..', 'fragments', 'imageFragments.js'),
      `${program.directory}/.cache/fragments/sanity-image-fragments.js`,
    )
  }
}

const resolveReferencesConfig = new GraphQLInputObjectType({
  name: 'SanityResolveReferencesConfiguration',
  fields: {
    maxDepth: {
      type: new GraphQLNonNull(GraphQLInt),
      description: 'Max depth to resolve references to',
    },
  },
})

export const setFieldsOnGraphQLNodeType = async (
  context: GatsbyContext & GatsbyOnNodeTypeContext,
  pluginConfig: PluginConfig,
) => {
  const {type} = context
  const typeMapKey = getCacheKey(pluginConfig, CACHE_KEYS.TYPE_MAP)
  const typeMap = (stateCache[typeMapKey] || defaultTypeMap) as TypeMap
  const schemaType = typeMap.objects[type.name]

  let fields: {[key: string]: GraphQLFieldConfig} = {}

switch (field.type) {
    case 'Color':
    case 'Select':
    case 'Text':
    case 'UID':
      return { type: new GraphQLNonNull(GraphQLString) }

    case 'StructuredText':
      return { type: GraphQLPrismicHTML }

    case 'Number':
      return { type: new GraphQLNonNull(GraphQLFloat) }

    case 'Date':
    case 'Timestamp':
      return { type: new GraphQLNonNull(GraphQLDate) }

    case 'GeoPoint':
      return { type: GraphQLPrismicGeoPoint }

    case 'Embed':
      return { type: GraphQLPrismicEmbed }

    case 'Image':
      return { type: GraphQLPrismicImage }

    case 'Link':
      return { type: GraphQLPrismicLink }

    case 'Group':
      const group = R.pipe(
        R.path(['config', 'fields']),

provider_name: { type: new GraphQLNonNull(GraphQLString) },
    provider_url: { type: new GraphQLNonNull(GraphQLString) },
    thumbnail_height: { type: new GraphQLNonNull(GraphQLString) },
    thumbnail_url: { type: new GraphQLNonNull(GraphQLString) },
    thumbnail_width: { type: new GraphQLNonNull(GraphQLString) },
    title: { type: new GraphQLNonNull(GraphQLString) },
    type: { type: new GraphQLNonNull(GraphQLString) },
    version: { type: new GraphQLNonNull(GraphQLString) },
  },
})

const GraphQLPrismicImageDimensions = new GraphQLObjectType({
  name: generateNamespacedTypeName('Image', 'Dimensions'),
  fields: {
    width: { type: new GraphQLNonNull(GraphQLInt) },
    height: { type: new GraphQLNonNull(GraphQLInt) },
  },
})

const GraphQLPrismicImage = new GraphQLObjectType({
  name: generateNamespacedTypeName('Image'),
  fields: {
    alt: { type: new GraphQLNonNull(GraphQLString) },
    copyright: { type: new GraphQLNonNull(GraphQLString) },
    dimensions: { type: GraphQLPrismicImageDimensions },
    url: { type: GraphQLImageURL },
  },
})

const GraphQLPrismicLink = new GraphQLObjectType({
  name: generateNamespacedTypeName('Link'),
  fields: {