docs: public QueryResultMapper<?> mapperFor(String name, Map<String, String> columnMapping) {
          if (!knownMappers.containsKey(name)) {
              throw new IllegalArgumentException("No mapper found with name " + name);
          }
          if (columnMapping == null) {
              return knownMappers.get(name);
          } else {
              return knownMappers.get(name).forColumnMapping(columnMapping);
          }
      }