code: public void appendAttribute(final Appendable appendable,
                                  final CharSequence attrName, final boolean attrValue) throws IOException {
  		this.appendAttribute(appendable, attrName,
  				Boolean.toString(attrValue));
  	}
docs: Append a new element to the appendable element, the name of the element is
  attrName and the value is the boolean attrValue.
  
  @param appendable The StringBuilder to which the new element should be added.
  @param attrName   The new element name
  @param attrValue  The value of the element
  @throws IOException If an I/O error occurs