This pull request adds a new test for the decision tree visualization functionality. The test ensures that the printed representation of a sample decision tree matches the expected output.

Testing improvements:

• Added a new test, test_show_tree, in tests/decisiontree/test_visualize.py to verify that the show_tree function outputs the correct tree structure using a sample decision tree and output snapshot comparison.
• Introduced a sample_decision_tree pytest fixture to provide a reusable sample tree for testing purposes.