input: 
  from typing import Any
  
  class HashTable:
      """A simple hash table implementation with support for insert, delete, and retrieve operations.
      The table uses chaining to handle collisions.
      
      Examples:
      >>> ht = HashTable()
      >>> ht.insert('key1', 'value1')
      >>> ht.retrieve('key1')
      'value1'
      >>> ht.delete('key1')
      >>> ht.retrieve('key1')
      """
  
      def __init__(self):
          self.table = [[] for _ in range(256)]
   
      def insert(self, key: Any, value: Any):
          h = hash(key) % 256
          for i, kv in enumerate(self.table[h]):
              if kv[0] == key:
                  self.table[h][i] = (key, value)
                  return
          self.table[h].append((key, value))
   
      def retrieve(self, key: Any) -> Any:
          h = hash(key) % 256
          for kv in self.table[h]:
              if kv[0] == key:
                  return kv[1]
   
      def delete(self, key: Any):
          h = hash(key) % 256
          for i, kv in enumerate(self.table[h]):
              if kv[0] == key:
                  del self.table[h][i]
                  return
  
output:     
          return None
  