<SYSTEM_TASK:>
Given the following text description, write Python code to implement the functionality described below step by step
<END_TASK>
<USER_TASK:>
Description:
 <small><i>This notebook was prepared by Donne Martin. Source and license info is on GitHub.</i></small>
Challenge Notebook
Problem
Step1:  Unit Test
<ASSISTANT_TASK:>
Python Code:
%run ../bst/bst.py
%load ../bst/bst.py
def in_order_traversal(node, visit_func):
    # TODO: Implement me
    pass
def pre_order_traversal(node, visit_func):
    # TODO: Implement me
    pass
def post_order_traversal(node, visit_func):
    # TODO: Implement me
    pass
Explanation: <small><i>This notebook was prepared by Donne Martin. Source and license info is on GitHub.</i></small>
Challenge Notebook
Problem: Implement depth-first searches (in-order, pre-order, post-order traversals) on a binary tree.
Constraints
Test Cases
Algorithm
Code
Unit Test
Constraints
Can we assume we already have a Node class with an insert method?
Yes
Test Cases
In-Order Traversal
5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8
1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5
Pre-Order Traversal
5, 2, 8, 1, 3 -> 5, 2, 1, 3, 8
1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5
Post-Order Traversal
5, 2, 8, 1, 3 -> 1, 3, 2, 8, 5
1, 2, 3, 4, 5 -> 5, 4, 3, 2, 1
Algorithm
Refer to the Solution Notebook.  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.
Code
End of explanation
%run ../utils/results.py
# %load test_dfs.py
from nose.tools import assert_equal
class TestDfs(object):
    def __init__(self):
        self.results = Results()
    def test_dfs(self):
        node = Node(5)
        insert(node, 2)
        insert(node, 8)
        insert(node, 1)
        insert(node, 3)
        in_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[1, 2, 3, 5, 8]")
        self.results.clear_results()
        pre_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[5, 2, 1, 3, 8]")
        self.results.clear_results()
        post_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[1, 3, 2, 8, 5]")
        self.results.clear_results()
        node = Node(1)
        insert(node, 2)
        insert(node, 3)
        insert(node, 4)
        insert(node, 5)
        in_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[1, 2, 3, 4, 5]")
        self.results.clear_results()
        pre_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[1, 2, 3, 4, 5]")
        self.results.clear_results()
        post_order_traversal(node, self.results.add_result)
        assert_equal(str(self.results), "[5, 4, 3, 2, 1]")
        print('Success: test_dfs')
def main():
    test = TestDfs()
    test.test_dfs()
if __name__ == '__main__':
    main()
Explanation: Unit Test
End of explanation
<END_TASK>