input: Write a function to extract verbs from a given sentence using the NLTK library. The function should return a list of verbs found in the sentence. If no verbs are found, it should return an empty list.
  assert extract_verbs("The cat jumped over the moon.")==['jumped']
  assert extract_verbs("She eats apples every day.")==['eats', 'apples', 'every', 'day']
  assert extract_verbs("Beautiful flowers are blooming")==['are', 'blooming']
  assert extract_verbs("A quiet and peaceful night")==[]
output: def extract_verbs(sentence):
      from nltk import word_tokenize, pos_tag
      words = word_tokenize(sentence)
      tagged = pos_tag(words)
      verbs = [word for word, pos in tagged if pos.startswith('VB')]
      return verbs