code: private static String convertMap(String ref, TypeDef source, TypeDef target) {
          Method ctor = BuilderUtils.findBuildableConstructor(target);
          String arguments = ctor.getArguments().stream()
                  .map(p -> readMapValue(ref, source, p))
                  .collect(joining(",\n","\n", ""));
  
          StringBuilder sb = new StringBuilder();
          sb.append("new ").append(target.getFullyQualifiedName()).append("(").append(arguments).append(")");
          return sb.toString();
      }
docs: Converts a map describing the source type, to the target.
  @param ref               The ref.
  @param source            The source type of the reference..
  @param target            The target type.
  @return