code: 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);
          }
      }
docs: Returns mapper for given name if found
  @param name unique name that mapper is bound to
  @param columnMapping provides column mapping (name to type) that can be
  shipped to mapper for improved transformation - can be null (accepted types: string, long, integer, date, double)
  @return instance of the <code>QueryResultMapper</code> if found
  @throws IllegalArgumentException in case there is no mapper found with given name