code: def test_nanmax_all_nan(self, xp, dtype):
      a = xp.array([float("nan"), float("nan")], dtype)
      with warnings.catch_warnings(record=True) as w:
          warnings.simplefilter("always")
          m = xp.nanmax(a)
      assert len(w) == 1
      assert w[0].category is RuntimeWarning
      return m
  
imports: import warnings
  import numpy
  import pytest
  import cupy
  import cupy._core._accelerator
  from cupy import cuda
  from cupy import testing
label_desc: Use image node_id 7 for calling the TestOrder obj's underlying member method code with example usage: obj.test_nanmax_all_nan(xp, dtype) and returns: m