input: Write a python function to classify a sentence as 'positive' or 'negative'.
  assert classify_sentence("The movie was great!") == 'positive'
  assert classify_sentence("I hated the food.") == 'negative'
  assert classify_sentence("It was an average experience.") == 'neutral'
output: def classify_sentence(sentence):
      positive_keywords = ['great', 'awesome', 'fantastic', 'good', 'excellent', 'amazing']
      negative_keywords = ['hated', 'terrible', 'bad', 'awful', 'poor', 'worst']
      
      sentence_lower = sentence.lower()
      
      if any(keyword in sentence_lower for keyword in positive_keywords):
          return 'positive'
      elif any(keyword in sentence_lower for keyword in negative_keywords):
          return 'negative'
      else:
          return 'neutral'