input: from typing import Tuple
  
  def replace_string(sentence: str, old_word: str, new_word: str) -> Tuple[str, str]:
      """ Replace a given string with another string in the provided sentence.
      >>> replace_string("I love walking on the beach", "walking", "swimming")
      ('I love walking on the beach', 'I love swimming on the beach')
      >>> replace_string("The cat sat on the mat", "cat", "dog")
      ('The cat sat on the mat', 'The dog sat on the mat')
      """
      new_sentence = sentence.replace(old_word, new_word)
      return sentence, new_sentence
output:     new_sentence = sentence.replace(old_word, new_word)
      return sentence, new_sentence