code: def peekuntil(self, token, size=0):
          
          self.__append()
  
          i = self.buf.find(token, self.pos)
          if i < 0:
              index = max(len(token) - 1, size)
              newpos = max(len(self.buf) - index, self.pos)
              return False, self.buf[self.pos:newpos]
  
          newpos = i + len(token)
          return True, self.buf[self.pos:newpos]
docs: Peeks for token into the FIFO.
  
          Performs the same function as readuntil() without removing data from the
          FIFO. See readuntil() for further information.