code: public static Boolean selectBoolean(Node node,
                                          String xpath, Boolean defaultValue) {
          return selector.selectBoolean(node, xpath, defaultValue);
      }
docs: Extract a boolean value from {@code node} or return {@code defaultValue}
  if there is no boolean value at {@code xpath}
  
  @param node         the node with the wanted attribute.
  @param xpath        the path to extract.
  @param defaultValue the default value.
  @return the value of the path, if existing, else
  {@code defaultValue}