input: Write a python function to replace a specific word in a given text with another word.
  assert replace_word("The quick brown fox jumps over the lazy dog", "fox", "cat") == "The quick brown cat jumps over the lazy dog"
  assert replace_word("Hello world", "world", "everyone") == "Hello everyone"
  assert replace_word("Python is fun", "fun", "awesome") == "Python is awesome"
output: def replace_word(text, old_word, new_word):
      return text.replace(old_word, new_word)