input: from typing import List
  
  def extract_beats(music_string: str) -> List[int]:
      """ The input to this function is a string that represents musical notes in a unique ASCII format.
      Your task is to interpret this string and return a list of integers that indicate the number of beats each
      note lasts for.
  
      Here is a legend:
      'o' - whole note, lasts four beats
      'o|' - half note, lasts two beats
      '.|' - quarter note, lasts one beat
  
      >>> extract_beats('o o| .| o| o| .| .| .| .| o o')
      [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
      """
output:     mapping = {
          'o': 4,
          'o|': 2,
          '.|': 1
      }
  
      beats = []
      notes = music_string.split()
      
      for note in notes:
          if note in mapping:
              beats.append(mapping[note])
  
      return beats