code: def get_byte(self, index):
          
          pos = self.size() // 8 - 1 - index
          return self[pos * 8 + 7 : pos * 8]
docs: Extracts a byte from a BV, where the index refers to the byte in a big-endian order
  
          :param index: the byte to extract
          :return: An 8-bit BV