input: Write a python function to extract and return the names of reviewers who gave a rating of 4 or 5.
  assert extract_high_ratings({"Alice": {"rating": 5, "review": "Great!"}, "Bob": {"rating": 3, "review": "Okay"}}) == ["Alice"]
  assert extract_high_ratings({"John": {"rating": 4, "review": "Good"}, "Doe": {"rating": 2, "review": "Bad"}}) == ["John"]
  assert extract_high_ratings({"Jane": {"rating": 1, "review": "Terrible"}, "Smith": {"rating": 5, "review": "Excellent!"}}) == ["Smith"]
output: def extract_high_ratings(reviews):
      return [name for name, details in reviews.items() if details["rating"] in [4, 5]]