input: 
  # Below is an instruction that describes a task. Write a response that appropriately completes the request.
  
  from typing import List
  
  def replace_string(input_string: str, target_string: str, replacement_string: str) -> str:
      """ Replace all occurrences of the target_string in the input_string with the replacement_string.
      >>> replace_string("Hello World!", "World", "Python")
      'Hello Python!'
      >>> replace_string("Python is fun, isn't it?", "'", "-")
      "Python is fun, isn-t it?"
      """
  
output:     return input_string.replace(target_string, replacement_string)