input: Write a function to replace a given string with another string in a sentence. The function should take three parameters: the sentence, the word to be replaced, and the new word. If the word to be replaced is found in the sentence, it should be replaced with the new word and the updated sentence should be returned. If the word to be replaced is not found in the sentence, the original sentence should be returned unchanged.
  
  
  def replace_word_in_sentence(sentence, old_word, new_word):
      return sentence.replace(old_word, new_word)
  
  # Test cases
  assert replace_word_in_sentence("I love walking on the beach", "walking", "swimming") == "I love swimming on the beach"
  assert replace_word_in_sentence("Python is fun", "fun", "awesome") == "Python is awesome"
  assert replace_word_in_sentence("This is a test", "test", "") == "This is a "
  assert replace_word_in_sentence("No change here", "missing", "found") == "No change here"
  assert replace_word_in_sentence("", "anything", "nothing") == ""
  
output: def replace_word_in_sentence(sentence, old_word, new_word):
      return sentence.replace(old_word, new_word)