want to create a prefix tree in python (3)

2 ADTs Node and PrefixTree

Looking to create Node class with :

-__contains__(letter) - returns true if the Node has a child corresponding to the letter

-__getitem__(let) - returns the child node corresponding to the letter

-add_sub(tok, value) - adds a child to the node under the given token, also handle the case if a child already exists (it should only change the value of the child)

-remove_sub(let) - removes the child node corresponding to a given letter

this is the ADT:

class Node: def __init__(self, value = None): self.subs = {} self._value = value self.last = True