code: public String getString(final String fieldName) {
      try {
        return _jsonObject.getString(fieldName);
      } catch (JSONException ex) {
        throw new RuntimeException("Cannot find field", ex);
      }
    }
docs: Get a String field. Throws a QuandlRuntimeException if it cannot find the field
  
  @param fieldName the name of the field
  @return the field value, or null if the field is null