anchor.diff:     * Name of the configuration is stored under key "__name__".
      * Throws [ArgumentError] if configuration with [name] does not exists.
      */
  -  Map get(name) {
  +  Map get(String name) {
       return new ConfigMap(_get(name)).toMap();
     }
   
  -  Map _get(name) {
  +  Map _get(String name) {
       if (!_configurations.containsKey(name)) {
         throw new ArgumentError("Configuration with name '$name' does not exist.");
       }
  
positive.code:   getValue(config) => _computation(config);
  }
  
  $(dynamic computation(ConfigMap config)) => new ComputedValue(computation);
  
  class ConfigMap {
    ConfigMap root;
    Map _data;
  
negative.code: 
  library clean_config;
  
  /**
   * Recursively merges Map [b] into [a].
   *
   * If there are under a specific key distinct values in [a] and [b] which
   * are not Maps, the value in [b] is used.
   */
  Map mergeMaps(Map a, Map b) {
    a = new Map.from(a);
    b = new Map.from(b);
  