How to start with nodes collapsed?

[Jont828]

I would like to pass a field node.collapsed to load a specific node with its children collapsed. This way, for nodes with a ton of children, we can save some screen space. It looks like v-bind:collapsed="node.data._collapsed" and onClickNode() is responsible for setting node.data._collapsed and node.data.children to null. I'm thinking that I could initialize node.data._collapsed and node.data.children for nodes that I want collapsed to begin with. My question is, is there a function where it would make sense to add it?