code: def _digi_nan(fmt):
      
      if isinstance(fmt, list):
          return [_digi_nan(f) for f in fmt]
  
      if fmt == '80':
          return -128
      if fmt == '310':
          return -512
      if fmt == '311':
          return -512
      elif fmt == '212':
          return -2048
      elif fmt == '16':
          return -32768
      elif fmt == '61':
          return -32768
      elif fmt == '160':
          return -32768
      elif fmt == '24':
          return -8388608
      elif fmt == '32':
          return -2147483648
docs: Return the wfdb digital value used to store nan for the format type.
  
      Parmeters
      ---------
      fmt : str, or list
          The wfdb dat format, or a list of them.