code: def cf_data_to_bytes(value):
          
  
          start = CoreFoundation.CFDataGetBytePtr(value)
          num_bytes = CoreFoundation.CFDataGetLength(value)
          return string_at(start, num_bytes)
docs: Extracts a bytestring from a CFData object
  
          :param value:
              A CFData object
  
          :return:
              A byte string