code: function hasOutDatedTemplateCache (mainCompilation) {
    const childCompiler = getChildCompiler(mainCompilation.compiler);
    /**
     * @type {WeakMap<HtmlWebpackChildCompiler, boolean>|undefined}
     */
    let hasOutdatedChildCompilerDependenciesMap = hasOutdatedCompilationDependenciesMap.get(mainCompilation);
    // Create map for childCompiler if none exist
    if (!hasOutdatedChildCompilerDependenciesMap) {
      hasOutdatedChildCompilerDependenciesMap = new WeakMap();
      hasOutdatedCompilationDependenciesMap.set(mainCompilation, hasOutdatedChildCompilerDependenciesMap);
    }
    // Try to get the `checkChildCompilerCache` result from cache
    let isOutdated = hasOutdatedChildCompilerDependenciesMap.get(childCompiler);
    if (isOutdated !== undefined) {
      return isOutdated;
    }
    // If `checkChildCompilerCache` has never been called for the given
    // `mainCompilation` and `childCompiler` combination call it:
    isOutdated = isChildCompilerCacheOutdated(mainCompilation, childCompiler);
    hasOutdatedChildCompilerDependenciesMap.set(childCompiler, isOutdated);
    return isOutdated;
  }
docs: Returns `true` if the file dependencies of the current childCompiler
  for the given mainCompilation are outdated.
  
  Uses the `hasOutdatedCompilationDependenciesMap` cache if possible.
  
  @param {WebpackCompilation} mainCompilation
  @returns {boolean}