(Naive) Python Implementation of Trie

trie.py

from __future__ import annotations

class TrieNode:
    
    def __init__(self, char: str):
        self.char = char
        self.is_end = False
        self.children = {}
        
    def add_child(self, char: str) -> None:
        if char not in self.children:
            self.children[char] = TrieNode(char)
    
    def get_child(self, char: str) -> Union[TrieNode, None]:
        return self.children.get(char, None)
            
    def end(self) -> None:
        self.is_end = True
        
class Trie:
    
    def __init__(self):
        self.root = TrieNode("")
    
    def add(self, keyword: str):
        if keyword:
            node = self.root
            for char in list(keyword):
                node.add_child(char)
                node = node.get_child(char)
            node.end()
                
    def query(self, text: str) -> list[str]:
        keyword_matched = []
        for i in range(len(text)):
            node = self.root
            text_sub = text[i:]
            for j, char in enumerate(text_sub):
                node = node.get_child(char)
                if node is None:
                    break
                elif node.is_end:
                    keyword_matched.append(text_sub[:j+1])
        return keyword_matched