def find_subtree(tree, node_id):
    """
    Recurse through the tree until the node is found
    Then return the node

    Args:
        tree: Node containing full tree
        node_id: string id directing which nodes to traverse

    Returns:
        Node containing full tree
    """
    # We have reached the correct node if the string is empty
    if node_id == "":
        # Return the tree node
        return tree

    # This gets casted to an integer so it can be used as an index
    node_index = int(node_id[0])
    # The next node is the correct node if the length of the node_id is 1
    if len(node_id) == 1:
        next_id = ""
    else:
        next_id = node_id[1:]

    # Return the recursive call
    return find_subtree(tree.args[node_index], next_id)