code: public Boolean getBoolean(String attributeName) {
          Object value = getRaw(attributeName);
          Converter<Object, Boolean> converter = modelRegistryLocal.converterForValue(attributeName, value, Boolean.class);
          return converter != null ? converter.convert(value) : Convert.toBoolean(value);
      }
docs: Gets attribute value as <code>Boolean</code>.
  If there is a {@link Converter} registered for the attribute that converts from Class <code>S</code> to Class
  <code>java.lang.Boolean</code>, given the attribute value is an instance of <code>S</code>, then it will be used,
  otherwise performs a conversion using {@link Convert#toBoolean(Object)}.
  
  @param attributeName name of attribute to convert
  @return value converted to <code>Boolean</code>