backward method

void backward()

Implementation

void backward() {
  var topo = [];
  Set<Value> visited = {};
  topo = _buildTopoOrder(this, visited, topo);

  grad = 1;
  for (var idx = topo.length - 1; idx >= 0; idx--) {
    var val = topo[idx];
    val._backwardFn();
  }
}