code: def test_conversion(self):
      half = internal.to_float16(float("nan"))
      assert math.isnan(internal.from_float16(half))
  
imports: import math
  import unittest
  import numpy
  import pytest
  from cupy._core import internal
  from cupy import testing
label_desc: Use image node_id 1 for calling the TestConvertFloat16Nan obj's underlying member method code with example usage: obj.test_conversion() without return types