code: public static boolean isSanitizedContentMap(FieldDescriptor fieldDescriptor) {
      if (!fieldDescriptor.isMapField()) {
        return false;
      }
      Descriptor valueDesc = getMapValueMessageType(fieldDescriptor);
      if (valueDesc == null) {
        return false;
      }
      return SAFE_PROTO_TYPES.contains(valueDesc.getFullName());
    }
docs: Returns true if fieldDescriptor holds a map where the values are a sanitized proto type.