input: Write a python function to categorize sentences based on their sentiment.
  assert categorize_sentences(["I feel great", "This is terrible", "I'm not sure about this", "I don't know"]) == ["positive", "negative", "unknown", "unknown"]
  assert categorize_sentences(["She is very happy", "He is sad", "This is neutral", "What a great day!"]) == ["positive", "negative", "neutral", "positive"]
  assert categorize_sentences(["It's a terrible mistake", "I'm happy with the result", "Don't know what to say", "This is not sure"]) == ["negative", "positive", "unknown", "unknown"]
output: def categorize_sentences(sentences):
      positive_words = ["great", "happy", "great day", "happy with"]
      negative_words = ["terrible", "sad", "terrible mistake"]
      neutral_words = ["neutral"]
      unknown_words = ["not sure", "don't know", "don't know what to say"]
  
      categorized = []
      for sentence in sentences:
          sentence_lower = sentence.lower()
          if any(word in sentence_lower for word in positive_words):
              categorized.append("positive")
          elif any(word in sentence_lower for word in negative_words):
              categorized.append("negative")
          elif any(word in sentence_lower for word in neutral_words):
              categorized.append("neutral")
          elif any(word in sentence_lower for word in unknown_words):
              categorized.append("unknown")
          else:
              categorized.append("unknown")
      
      return categorized