validations:
      required: true

  - type: textarea
    attributes:
      label: Actual Behavior
      description: What actually happened?
    validations:
      required: true

  - type: dropdown
    attributes:
      label: Packages
      description: If this issue is package-specific, then please select the relevant packages.
      multiple: true
      options:
        - com.google.common.annotations

  - type: textarea
    attributes:
      label: Concrete Use Cases
      description: Please provide use cases that actually came up in the real world.
    validations:
      required: true

  - type: dropdown
    attributes:
      label: Packages
      description: Please select all of the packages that are relevant to this feature request.
      multiple: true
      options:
        - com.google.common.annotations

          return null;
        }
      };
    }

    final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) {
      return topDown(startNodes, InsertionOrder.BACK);
    }

    final Iterator<N> preOrder(Iterator<? extends N> startNodes) {
      return topDown(startNodes, InsertionOrder.FRONT);
    }

    /**
     * In top-down traversal, an ancestor node is always traversed before any of its descendant