I know about onChange for events on elements. But what exactly is it doing on the cursor? onChange in react allows you to provide a callback when things change. But that doesn't appear to be what is happening with the code samples in the read me.
For example
cursor.refine('b').refine('foo').onChange({ 'bar': 43, baz: 56 })
What is this doing? If onChange isn't transact, what is the react-cursor equivalent?