code: def _single_round(self, counter, key):
      lo0, hi0 = self._multiply_low_high(
          self._config.PHILOX_ROUND_A, counter[0]
      )
      lo1, hi1 = self._multiply_low_high(
          self._config.PHILOX_ROUND_B, counter[2]
      )
      ret0 = hi1 ^ counter[1] ^ key[0]
      ret1 = lo1
      ret2 = hi0 ^ counter[3] ^ key[1]
      ret3 = lo0
      return np.array([ret0, ret1, ret2, ret3], dtype=self._dtype)
  
imports: import numpy
  import pytest
  import scipy.stats
  import torch
  import triton
  import triton.language
label_desc: Use image node_id 5 for calling the CustomPhilox4x obj's underlying member method code with example usage: obj._single_round(counter, key) and returns: np