Write the code for the smaller() method in Python 3.7 language:

class BinarySearchTree: ""Binary Search Tree class. This class represents a binary tree satisfying the Binary Search Tree property: for every node, its value is all items stored in its left subtree, and -self-root. def smaller(self, item: Any) ->List: """Return all of the items in this BST strictly smaller than The items are returned in sorted order. Precondition: all items in this BST can be compared with . As with BinarySearchTree.items, you should *not* need to sort the list yourself! >>bst - BinarySearchTree(7) >leftBinarySearchTree(3) >>> eft.-left = BinarySearchTree ( 2 ) >>left._rightBinarySearchTree(5) >>rightBinarySearchTree(11) >>>right._left-BinarySearchTree(9) >>>right._right-BinarySearchTree(13) >bst._left -left >>> bst-right = right >>bst.smaller(6) [2, 3, 5] >>bst.smaller (13) [2, 3, 5, 7, 9, 11] if self.is_empty): return [] # ADD CODE HERE class BinarySearchTree: ""Binary Search Tree class. This class represents a binary tree satisfying the Binary Search Tree property: for every node, its value is all items stored in its left subtree, and -self-root. def smaller(self, item: Any) ->List: """Return all of the items in this BST strictly smaller than The items are returned in sorted order. Precondition: all items in this BST can be compared with . As with BinarySearchTree.items, you should *not* need to sort the list yourself! >>bst - BinarySearchTree(7) >leftBinarySearchTree(3) >>> eft.-left = BinarySearchTree ( 2 ) >>left._rightBinarySearchTree(5) >>rightBinarySearchTree(11) >>>right._left-BinarySearchTree(9) >>>right._right-BinarySearchTree(13) >bst._left -left >>> bst-right = right >>bst.smaller(6) [2, 3, 5] >>bst.smaller (13) [2, 3, 5, 7, 9, 11] if self.is_empty): return [] # ADD CODE HERE