Python Toolbox Field Mappings parameter behaviour

Hi guys,

I'm a newbie in Python toolbox creation. After sometimes researching on internet, I could not found the right example for Field Mapping parameter behavior.

I really wants to know how is Append_Management toolbox field mapping works specially in UpdateParameters function.

I'm using ArcGIS Desktop 10.1, Python 2.7.

If anyone have any reference and sample of Python toolbox with Field Mappings behavior, will be highly appreaciated.