Fix type annotations for trie.py

Author: archaengel

data_structures/trie/trie.py

@@ -5,13 +5,15 @@
 longest word)) lookup time making it an optimal approach when space is not an issue.
 """
 
+from typing import List
+
 
 class TrieNode:
     def __init__(self):
         self.nodes = dict()  # Mapping from char to TrieNode
         self.is_leaf = False
 
-    def insert_many(self, words: [str]):
+    def insert_many(self, words: List[str]):
         """
         Inserts a list of words into the Trie
         :param words: list of string words