code: private List<Integer> indicesOf(@Nullable final Set<String> values) {
          List<Integer> indices = new ArrayList<>();
  
          if (values != null && getEntryValues() != null) {
              for (String value : values) {
                  int index = indexOf(value);
  
                  if (index >= 0) {
                      indices.add(index);
                  }
              }
          }
  
          return indices;
      }
docs: Return the indices of the entries, which correspond to specific values.
  
  @param values
  A set, which contains the values of the entries, whose indices should be returned, as
  an instance of the type {@link Set}
  @return A list, which contains the indices of the entries, the given values correspond to, as
  an instance of the type {@link List}