public void Can_calculate_leaf_index_from_node_index(ulong nodeIndex, uint?leafIndex)
 {
     if (leafIndex == null)
     {
         Assert.Throws <ArgumentOutOfRangeException>(() => BaselineTree.GetLeafIndex(nodeIndex));
     }
     else
     {
         BaselineTree.GetLeafIndex(nodeIndex).Should().Be(leafIndex.Value);
     }
 }