How to use the @fortawesome/fontawesome-svg-core.layer function in @fortawesome/fontawesome-svg-core

const { layer: faLayer, icon: faIcon, dom: faDom, library: faLibrary } = require('@fortawesome/fontawesome-svg-core')
const { faCircle, faInfoCircle, faExclamationCircle, faQuestionCircle, faExclamationTriangle, faHandPaper, fas } = require('@fortawesome/free-solid-svg-icons')
const { faLightbulb, far } = require('@fortawesome/free-regular-svg-icons')
const { fab } = require('@fortawesome/free-brands-svg-icons')
faLibrary.add(fas, far, fab)

const faDefaultIcon = faIcon(faQuestionCircle)
const faImportantIcon = faIcon(faExclamationCircle)
const faNoteIcon = faIcon(faInfoCircle)
const faWarningIcon = faIcon(faExclamationTriangle)
const faCautionIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faHandPaper, { transform: { size: 10, x: -0.5 }, classes: 'fa-inverse' }))
})
const faTipIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faLightbulb, { transform: { size: 10 }, classes: 'fa-inverse' }))
})

const repeatTableHeadersContent = fs.readFileSync(`${__dirname}/repeating-table-headers.js`, 'utf8')
const pagedContent = fs.readFileSync(require.resolve('pagedjs/dist/paged.polyfill.js'), 'utf8')
const pagedRendering = fs.readFileSync(`${__dirname}/paged-rendering.js`, 'utf8')
const stylesDirectoryPath = ospath.resolve(`${__dirname}/../../css`)
const asciidoctorStyleContent = fs.readFileSync(`${stylesDirectoryPath}/asciidoctor.css`, 'utf8')
const documentStyleContent = fs.readFileSync(`${stylesDirectoryPath}/document.css`, 'utf8')
const titleDocumentStyleContent = fs.readFileSync(`${stylesDirectoryPath}/features/title-document-numbering.css`, 'utf8')
const titlePageStyleContent = fs.readFileSync(`${stylesDirectoryPath}/features/title-page-numbering.css`, 'utf8')
const bookStyleContent = fs.readFileSync(`${stylesDirectoryPath}/features/book.css`, 'utf8')

const resolveStylesheet = (requirePath, cwd = process.cwd()) => {
  // NOTE appending node_modules prevents require from looking elsewhere before looking in these paths

/* global Opal */
const fs = require('fs')
const ospath = require('path')
const stemContent = require('./stem')

const { layer: faLayer, icon: faIcon, dom: faDom, library: faLibrary } = require('@fortawesome/fontawesome-svg-core')
const { faCircle, faInfoCircle, faExclamationCircle, faQuestionCircle, faExclamationTriangle, faHandPaper, fas } = require('@fortawesome/free-solid-svg-icons')
const { faLightbulb, far } = require('@fortawesome/free-regular-svg-icons')
const { fab } = require('@fortawesome/free-brands-svg-icons')
faLibrary.add(fas, far, fab)

const faDefaultIcon = faIcon(faQuestionCircle)
const faImportantIcon = faIcon(faExclamationCircle)
const faNoteIcon = faIcon(faInfoCircle)
const faWarningIcon = faIcon(faExclamationTriangle)
const faCautionIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faHandPaper, { transform: { size: 10, x: -0.5 }, classes: 'fa-inverse' }))
})
const faTipIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faLightbulb, { transform: { size: 10 }, classes: 'fa-inverse' }))
})

const repeatTableHeadersContent = fs.readFileSync(`${__dirname}/repeating-table-headers.js`, 'utf8')
const pagedContent = fs.readFileSync(require.resolve('pagedjs/dist/paged.polyfill.js'), 'utf8')
const pagedRendering = fs.readFileSync(`${__dirname}/paged-rendering.js`, 'utf8')
const stylesDirectoryPath = ospath.resolve(`${__dirname}/../../css`)
const asciidoctorStyleContent = fs.readFileSync(`${stylesDirectoryPath}/asciidoctor.css`, 'utf8')
const documentStyleContent = fs.readFileSync(`${stylesDirectoryPath}/document.css`, 'utf8')
const titleDocumentStyleContent = fs.readFileSync(`${stylesDirectoryPath}/features/title-document-numbering.css`, 'utf8')
const titlePageStyleContent = fs.readFileSync(`${stylesDirectoryPath}/features/title-page-numbering.css`, 'utf8')

const { layer: faLayer, icon: faIcon, dom: faDom, library: faLibrary } = require('@fortawesome/fontawesome-svg-core')
const { faCircle, faInfoCircle, faExclamationCircle, faQuestionCircle, faExclamationTriangle, faHandPaper, fas } = require('@fortawesome/free-solid-svg-icons')
const { faLightbulb, far } = require('@fortawesome/free-regular-svg-icons')
const { fab } = require('@fortawesome/free-brands-svg-icons')
faLibrary.add(fas, far, fab)

const faDefaultIcon = faIcon(faQuestionCircle)
const faImportantIcon = faIcon(faExclamationCircle)
const faNoteIcon = faIcon(faInfoCircle)
const faWarningIcon = faIcon(faExclamationTriangle)
const faCautionIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faHandPaper, {transform: { size: 10, x: -0.5 }}))

})
const faTipIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faLightbulb, {transform: { size: 10 }}))
})

const isSvgIconEnabled = (node) => node.getDocument().isAttribute('icontype', 'svg') || node.getDocument().isAttribute('icons', 'font')

const fontAwesomeStyleContent = (node) => {
  if (isSvgIconEnabled(node)) {
    return faDom.css()
  }
  return ''

const { layer: faLayer, icon: faIcon, dom: faDom, library: faLibrary } = require('@fortawesome/fontawesome-svg-core')
const { faCircle, faInfoCircle, faExclamationCircle, faQuestionCircle, faExclamationTriangle, faHandPaper, fas } = require('@fortawesome/free-solid-svg-icons')
const { faLightbulb, far } = require('@fortawesome/free-regular-svg-icons')
const { fab } = require('@fortawesome/free-brands-svg-icons')
faLibrary.add(fas, far, fab)

const faDefaultIcon = faIcon(faQuestionCircle)
const faImportantIcon = faIcon(faExclamationCircle)
const faNoteIcon = faIcon(faInfoCircle)
const faWarningIcon = faIcon(faExclamationTriangle)
const faCautionIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faHandPaper, {transform: { size: 10, x: -0.5 }}))

})
const faTipIcon = faLayer((push) => {
  push(faIcon(faCircle))
  push(faIcon(faLightbulb, {transform: { size: 10 }}))
})

const isSvgIconEnabled = (node) => node.getDocument().isAttribute('icontype', 'svg') || node.getDocument().isAttribute('icons', 'font')

const fontAwesomeStyleContent = (node) => {
  if (isSvgIconEnabled(node)) {
    return faDom.css()
  }
  return ''
}

const assetUriScheme = (node) => {
  let result = node.getAttribute('asset-uri-scheme', 'https')
  if (result.trim() !== '') {