Insert a tree before Nth child of the given tree. The tree is inserted so
that it becomes the Nth child of the tree, and the previous Nth child becomes
moves over to position N+1.
Negative indexes are handled as offsets from the final tree in the forest so
that inserting a tree to index -1 inserts the tree before the last
tree of the forest. Use append to append after the last tree.
If self is a leaf, it is converted into a branch.
If the index is out-of-bounds, I.E.: negative or greater than `forest length
1`, the tree is appended to the end of the forest.
Insert a tree before Nth child of the given tree. The tree is inserted so that it becomes the Nth child of the tree, and the previous Nth child becomes moves over to position N+1.
Negative indexes are handled as offsets from the final tree in the forest so that inserting a tree to index
-1inserts the tree before the last tree of the forest. Use append to append after the last tree.If
selfis a leaf, it is converted into a branch.If the index is out-of-bounds, I.E.: negative or greater than `forest length