input: Write a function to analyze the sentiment of given text. The function should categorize the text into positive, negative, and neutral sentiments. If the sentiment analysis is more negative than positive, return 'negative'. If it is more positive than negative, return 'positive'. If negative and positive are equal, return 'neutral'.
  assert analyze_sentiment("I am very happy today.") == 'positive'
  assert analyze_sentiment("I feel sad and upset.") == 'negative'
  assert analyze_sentiment("Everything is fine.") == 'neutral'
  assert analyze_sentiment("I don't feel any emotion.") == 'neutral'
  assert analyze_sentiment("This strange mixture of joy and sadness.") == 'neutral'
output: def analyze_sentiment(text):
      positive_words = ['happy', 'joy', 'fine', 'positive', 'joyful']
      negative_words = ['sad', 'upset', 'negative', 'unhappy', 'sadness']
      
      positive_count = sum(1 for word in text.split() if word.lower() in positive_words)
      negative_count = sum(1 for word in text.split() if word.lower() in negative_words)
      
      if positive_count > negative_count:
          return 'positive'
      elif negative_count > positive_count:
          return 'negative'
      else:
          return 'neutral'