class Node:
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right


def inorder(node, result=None):
    if result is None:
        result = []
    if node is None:
        return result
    inorder(node.left, result)
    result.append(node.value)
    inorder(node.right, result)
    return result


# Tree: root 8; left child 3, right child 10.
# 3's children are 1 and 6; 6's children are 4 and 7.
# 10's right child is 14, and 14's left child is 13.
root = Node(8,
            Node(3, Node(1), Node(6, Node(4), Node(7))),
            Node(10, None, Node(14, Node(13))))

print(inorder(root))
# [1, 3, 4, 6, 7, 8, 10, 13, 14]