class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []

    def add_child(self, child_node):
        self.children.append(child_node)

# Build a small company org chart
ceo = TreeNode('CEO')
cto = TreeNode('CTO')
cfo = TreeNode('CFO')
ceo.add_child(cto)
ceo.add_child(cfo)
cto.add_child(TreeNode('Engineering Manager'))

print(ceo.value)                       # CEO
print([child.value for child in ceo.children])  # ['CTO', 'CFO']