def _walk_equal(bstree_left, bstree_right):
    """
    Compare every node using recursive, once two node are not equal, return
    False, or return True.

    Args:
        bstree_left: a Node object
        bstree_right: a Node object

    Returns:
        True: two BinarySearchTree are equal
        False: two BinarySearchTree are not equal
    """

    ptr_left = bstree_left
    ptr_right = bstree_right

    if ptr_left and ptr_right:
        compare_val = ptr_left.value == ptr_right.value
        compare_left = _walk_equal(ptr_left.left, ptr_right.left)
        compare_right = _walk_equal(ptr_left.right, ptr_right.right)
        return compare_val and compare_left and compare_right
    return ptr_left == ptr_right