input: Write a function to replace a given word in a sentence with another word, then print the new sentence. The function should take three parameters: the original sentence, the word to be replaced, and the new word.
  def replace_word(sentence, old_word, new_word):
      return sentence.replace(old_word, new_word)
  
  assert replace_word("I love walking on the beach", "walking", "swimming") == "I love swimming on the beach"
  assert replace_word("Python is a great language", "Python", "Java") == "Java is a great language"
  assert replace_word("She reads books every day", "reads", "writes") == "She writes books every day"
  assert replace_word("The cat is sleeping on the mat", "cat", "dog") == "The dog is sleeping on the mat"
  assert replace_word("", "any", "thing") == ""
output: def replace_word(sentence, old_word, new_word):
      return sentence.replace(old_word, new_word)