input: Write a python function to perform sentiment analysis on a given sentence.
  assert sentiment_analysis("I love sunny days!") == "positive"
  assert sentiment_analysis("It is an average day.") == "neutral"
  assert sentiment_analysis("I hate getting wet in the rain.") == "negative"
output: def sentiment_analysis(sentence):
      positive_words = ["love", "happy", "joy", "wonderful", "excellent", "good", "great", "sunny"]
      negative_words = ["hate", "sad", "bad", "terrible", "horrible", "poor", "negative", "wet"]
      
      sentence_lower = sentence.lower()
      positive_count = sum(word in sentence_lower for word in positive_words)
      negative_count = sum(word in sentence_lower for word in negative_words)
      
      if positive_count > negative_count:
          return "positive"
      elif negative_count > positive_count:
          return "negative"
      else:
          return "neutral"