code: public void assignDriver(XAttribute attribute, String driver) {
  		if (driver != null && driver.trim().length() > 0) {
  			XAttributeLiteral attr = (XAttributeLiteral) ATTR_DRIVER.clone();
  			attr.setValue(driver);
  			attribute.getAttributes().put(KEY_DRIVER, attr);
  		}
  	}
docs: Assigns any attribute its cost driver, as defined by this extension's
  driver attribute.
  
  @param attribute
  Attribute to assign cost driver to.
  @param driver
  The cost driver to be assigned.