class Node:
        def __init__(self, name=None, parent=None, available=True):
            self.name = name
            self.parent = parent
            self.available = available
            self.children = []
     
        def next_node(self):
            return None  # TODO


def print_tree(node, only_available=False):
    todo = [node]
    while todo:
        node = todo.pop()      
        if only_available and not node.available:
            continue
        todo.extend(reversed(node.children))
        print(node.name + (' (unavailable)' if not node.available else ''))


def traverse(node):
    while True:
        print(node.name)
        node = node.next_node()
        if not node:
            break


grandparent = Node(name='grandparent')
parent0 = Node(name='    parent0')
parent1 = Node(name='    parent1')
parent2 = Node(name='    parent2', available=False)
parent3 = Node(name='    parent3')
child0 = Node(name='        child0', available=False)
child1 = Node(name='        child1', available=False)
child2 = Node(name='        child2', available=False)
child3 = Node(name='        child3')
child4 = Node(name='        child4')
child5 = Node(name='        child5')
child6 = Node(name='        child6', available=False)
grandchild0 = Node(name='            grandchild0')
grandchild1 = Node(name='            grandchild1')
grandchild2 = Node(name='            grandchild2')
grandparent.children = [parent0, parent1, parent2, parent3]
parent0.children = [child0, child1]
parent1.children = [child2, child3]
parent2.children = [child4]
parent3.children = [child5, child6]
child0.children = [grandchild0, grandchild1]
child3.children = [grandchild2]
print('Full node tree:\n')
print_tree(grandparent, only_available=False)
print('\n\nGoal sequence:\n')
print_tree(grandparent, only_available=True)
print('\n\nTraverse using Node.next_node() method (must be equal to "Goal sequence"):\n')
traverse(grandparent)