code: public Object getAttributeValue(String attributeName) {
  		Attribute attribute = getAllAttributes().get(attributeName);
  		if (attribute != null) {
  			return attribute.getValue();
  		}
  		return null;
  	}
docs: Convenience method that returns the attribute value for the specified attribute name.
  
  @param attributeName the name of the attribute
  @return the value of the attribute or null if no such attribute exists
  @since 1.9.0