input: Write a function called extract_verbs that takes a sentence as an input string and returns a list of verbs extracted from the sentence. Use the nltk library for tokenization and POS tagging. Ensure that the function handles the input sentence properly and identifies all verbs in the sentence. Finally, print the list of verbs.
  
  assert extract_verbs("The cat jumped over the moon.")==['jumped']
output: def extract_verbs(sentence):
      from nltk import word_tokenize, pos_tag
      tokens = word_tokenize(sentence)
      tagged = pos_tag(tokens)
      verbs = [word for word, pos in tagged if pos.startswith('VB')]
      return verbs