function find (nodeById, id) {
    var node = nodeById.get(id)
    if (!node) throw new Error('missing: ' + id)
    return node
  }
function find (nodeById, id) {
    var node = nodeById.get(id)
    if (!node) throw new Error('missing: ' + id)
    return node
  }
function find ( nodeById , id ) { var node = nodeById . get ( id ) if ( ! node ) throw new Error ( 'missing: ' + id ) return node }
Return the node from the collection that matches the provided ID, or throw an error if no match
Return the node from the collection that matches the provided ID or throw an error if no match