input: Write a function to analyze the sentiment of given text and categorize it into positive, negative, and neutral sentiments. If the given text is empty then return 'neutral'.
  assert analyze_sentiment("I love this product so much!")=='positive'
  assert analyze_sentiment("I really hate this movie.")=='negative'
  assert analyze_sentiment("Weather is nice today.")=='neutral'
  assert analyze_sentiment("")=='neutral'
output: def analyze_sentiment(text):
      if not text:
          return 'neutral'
      positive_words = ['love', 'nice', 'so much']
      negative_words = ['hate', 'really hate']
      text_lower = text.lower()
      for word in positive_words:
          if word in text_lower:
              return 'positive'
      for word in negative_words:
          if word in text_lower:
              return 'negative'
      return 'neutral'