'Called when the state of any sub-parameter has changed.
**Arguments:**
param           The immediate child whose tree state has changed.
note that the change may have originated from a grandchild.
changes         List of tuples describing all changes that have been made
in this event: (param, changeDescr, data)
This function can be extended to react to tree state changes.'

def treeStateChanged(self, param, changes):

    self.treeStateChanges.extend(changes)
    self.emitTreeChanges()
