input: def extract_verbs(sentence: str) -> list:
      """ Extract and return only the verbs from a given sentence.
      >>> extract_verbs("The cat jumped over the moon.")
      ['jumped']
      >>> extract_verbs("She quickly ran to the store and bought some groceries.")
      ['ran', 'bought']
      """
output:     from nltk.tokenize import word_tokenize
      from nltk.tag import 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