code: def simplified_pos(pos, tagset=None):
      
      if tagset == 'penn':
          if pos.startswith('N') or pos.startswith('V'):
              return pos[0]
          elif pos.startswith('JJ'):
              return 'ADJ'
          elif pos.startswith('RB'):
              return 'ADV'
          else:
              return None
      else:   # default: WordNet, STTS or unknown
          if pos.startswith('N') or pos.startswith('V'):
              return pos[0]
          elif pos.startswith('ADJ') or pos.startswith('ADV'):
              return pos[:3]
          else:
              return None
docs: Return a simplified POS tag for a full POS tag `pos` belonging to a tagset `tagset`. By default the WordNet
      tagset is assumed.
      Does the following conversion by default:
      - all N... (noun) tags to 'N'
      - all V... (verb) tags to 'V'
      - all ADJ... (adjective) tags to 'ADJ'
      - all ADV... (adverb) tags to 'ADV'
      - all other to None
      Does the following conversion by with `tagset=='penn'`:
      - all N... (noun) tags to 'N'
      - all V... (verb) tags to 'V'
      - all JJ... (adjective) tags to 'ADJ'
      - all RB... (adverb) tags to 'ADV'
      - all other to None