docs: def decodeElem(self, bytes, index, raw=False):
          """Decodes a single element at array[index] from a sequence bytes
          that contain data for the entire array.
          """
          self._assertIndex(index)
          start = index * self.type.nbytes
          stop  = start + self.type.nbytes
  
          if stop > len(bytes):
              msg =  'Decoding %s[%d] requires %d bytes, '
              msg += 'but the ArrayType.decode() method received only %d bytes.'
              raise IndexError(msg % (self.type.name, index, stop, len(bytes)))
  
          return self.type.decode( bytes[start:stop], raw )