(4) X (2) | x To add the second 4 value, we need to determine to which x position this value will have to be attached according to the provided specifications. Going from the top to the bottom of the tree, the leftmost available position is the right child of the first 4 node. So we attach the second 4 there: | (2) 1 1 x x X The fourth value to be inserted into the binary tree is 8, and, obviously, the leftmost available position starting from the top of the tree is the left child of node 2. So this is where 8 is attached. | (2) (4) 1 (8) +--+--+ X X 3. Your implementation should support the in operator so that x in b where x is a value inserted into the binary_tree instance, b, using binary_tree.insert() method returns True . Similarly, e in b should return False if element e is not in binary tree instance, b. 4. binary_tree. iter__( self ): returns an iterator for the binary tree. The iterator must return the items in breadth-first order, meaning the items must be returned from top to bottom, and left-to-right order. Therefore, the iterator should always return the root node first, then the left child of the root node followed by the right child of the root node, and this behavior should continue in the same manner for the remaining descendants of the root node. This iterator must be implemented in the class bt_iterator. See the incomplete definition for this class below. You must implement your entire code without using any external libraries/modules. In other words, your code should have absolutely no functioning import statements in it! That is, even if your code works perfectly with import statements despite this requirement, your grade for this exam will unfortunately be zero. The instructor will check for the use of import statements in your code in an automated fashion that you will not have access to. So please do not take a chance with this. You must keep the file magic directive at the top of the following code cell. Do not remove this directive, as it will lead to the automatic failure of all test cases, which themselves will cause you to get a zero grade, even if your program happens to satisfy the remaining specifications. Note that any deviation from any of these specifications will cost you points. Failure to abide by the strict programming rules mentioned here will result in zero grade automatically. For example, even if your code uses a single import statement, you will get a grade of zero for your work, and such a case will also be closed for any sort of appeal later