function _cut(minimum, node, parent) {
    // remove node from parent children and decrement Degree[parent]
    node.left.right = node.right;
    node.right.left = node.left;
    parent.degree--; // reset y.child if necessary

    if (parent.child === node) {
      parent.child = node.right;
    } // remove child if degree is 0


    if (parent.degree === 0) {
      parent.child = null;
    } // add node to root list of heap


    node.left = minimum;
    node.right = minimum.right;
    minimum.right = node;
    node.right.left = node; // set parent[node] to null

    node.parent = null; // set mark[node] to false

    node.mark = false;
  }
The reverse of the link operation: removes node from the child list of parent.
This method assumes that min is non-null. Running time: O(1).
@memberof FibonacciHeap