improve doctest readability

data_structures/trie/radix_tree.py

@@ -54,6 +54,13 @@ class RadixNode:
             word (str): word to insert
 
         >>> RadixNode("myprefix").insert("mystring")
+
+        >>> root = RadixNode()
+        >>> root.insert_many(['myprefix', 'myprefixA', 'myprefixAA'])
+        >>> root.print_tree()
+        - myprefix   (leaf)
+        -- A   (leaf)
+        --- A   (leaf)
         """
         # Case 1: If the word is the prefix of the node
         # Solution: We set the current node as leaf