'Return an object that can be used to temporarily block and accumulate
sigTreeStateChanged signals. This is meant to be used when numerous changes are
about to be made to the tree and only one change signal should be
emitted at the end.
Example::
with param.treeChangeBlocker():
param.addChild(...)
param.removeChild(...)
param.setValue(...)'

def treeChangeBlocker(self):

    return SignalBlocker(self.blockTreeChangeSignal, self.unblockTreeChangeSignal)
