input: 
  import nltk
  
  def extract_verbs(sentence):
      """ Extracts and returns a list of verbs from a given sentence.
      >>> extract_verbs("The cat jumped over the moon.")
      ['jumped']
      >>> extract_verbs("She is running fast and laughing loudly.")
      ['is', 'running', 'laughing']
      """
      tokens = nltk.word_tokenize(sentence)
      tags = nltk.pos_tag(tokens)
      verbs = [word for word, pos in tags if pos.startswith('V')]
      return verbs
  
output:     tokens = nltk.word_tokenize(sentence)
      tags = nltk.pos_tag(tokens)
      verbs = [word for word, pos in tags if pos.startswith('V')]
      return verbs