input: Write a function to generate a Python program that takes a sentence as input and prints out only the verbs. Use the `nltk` library to tokenize the sentence and identify verbs. If the input sentence is empty, return an empty list.
  assert extract_verbs("The cat jumped over the moon.")==['jumped']
  assert extract_verbs("She is running fast.")==['is', 'running']
  assert extract_verbs("He eats lunch daily.")==['eats']
  assert extract_verbs("I love programming.")==['love']
  assert extract_verbs("")==[]
output: def extract_verbs(sentence):
      if not sentence:
          return []
      from nltk import word_tokenize, pos_tag
      words = word_tokenize(sentence)
      tagged_words = pos_tag(words)
      verbs = [word for word, pos in tagged_words if pos.startswith('VB')]
      return verbs