code: public Map<ClassInfo, ClassInfoList> getReverseClassDependencyMap() {
          final Map<ClassInfo, Set<ClassInfo>> revMapSet = new HashMap<>();
          for (final ClassInfo ci : getAllClasses()) {
              for (final ClassInfo dep : ci.getClassDependencies()) {
                  Set<ClassInfo> set = revMapSet.get(dep);
                  if (set == null) {
                      revMapSet.put(dep, set = new HashSet<ClassInfo>());
                  }
                  set.add(ci);
              }
          }
          final Map<ClassInfo, ClassInfoList> revMapList = new HashMap<>();
          for (final Entry<ClassInfo, Set<ClassInfo>> ent : revMapSet.entrySet()) {
              revMapList.put(ent.getKey(), new ClassInfoList(ent.getValue(), /* sortByName = */ true));
          }
          return revMapList;
      }
docs: Get the reverse class dependency map, i.e. a map from the {@link ClassInfo} object for each dependency class
  (whitelisted or not) to a list of the whitelisted classes that referenced that class as a dependency (i.e.
  returns a map from dependencies to dependents). Note that you need to call
  {@link ClassGraph#enableInterClassDependencies()} before {@link ClassGraph#scan()} for this method to work.
  You should also call {@link ClassGraph#enableExternalClasses()} before {@link ClassGraph#scan()} if you want
  non-whitelisted classes to appear in the result. See also {@link #getClassDependencyMap}.
  
  @return A map from a {@link ClassInfo} object for each dependency class (whitelisted or not) to a list of the
  whitelisted classes that referenced that class as a dependency (i.e. returns a map from dependencies
  to dependents).