Enhance BinaryTreeNode: Add type checking for child nodes

[apantzar]

Summary

This pull request introduces type checking to the setLeft and setRight methods of the BinaryTreeNode class. The enhancement ensures that only instances of BinaryTreeNode can be assigned as children, which prevents potential bugs caused by invalid node assignments.

Changes Made

• Added type checks to setLeft and setRight methods to ensure only BinaryTreeNode instances can be set as children.
• If an invalid node type is provided, an error is thrown to prevent incorrect usage.

Why This Change is Necessary

Type safety is crucial in maintaining the integrity of the binary tree structure. Without these checks, there's a risk of assigning incompatible objects as child nodes, which could lead to unexpected behavior or errors in tree operations.

Impact

These changes should not affect existing functionality but will enhance the robustness of the binary tree implementation.