input: Write a python function to classify a sentence into categories based on keywords.
  assert classify_sentence('The car is blue') == {'color': 'blue', 'object': 'car'}
  assert classify_sentence('A red apple') == {}
  assert classify_sentence('The blue sky and green grass') == {'color': 'blue'}
  assert classify_sentence('A car and a truck') == {'object': 'car'}
output: def classify_sentence(sentence):
      categories = {'color': ['blue', 'red', 'green'], 'object': ['car', 'truck']}
      result = {}
      
      for word in sentence.split():
          for category, keywords in categories.items():
              if word in keywords:
                  if category not in result:
                      result[category] = word
                  elif result[category] != word:
                      result[category] = word
      
      return result