Add isnan operator

[stever178]

pytest output:

=============================== test session starts ================================
platform linux -- Python 3.12.5, pytest-8.3.5, pluggy-1.5.0
rootdir: /home/lsj/projects/ntops
configfile: pyproject.toml
plugins: cov-6.1.1
collected 102 items

tests/test_abs.py ........                                                   [  7%]
tests/test_add.py ........                                                   [ 15%]
tests/test_addmm.py ..                                                       [ 17%]
tests/test_bmm.py ..                                                         [ 19%]
tests/test_cos.py ........                                                   [ 27%]
tests/test_div.py ........                                                   [ 35%]
tests/test_exp.py ........                                                   [ 43%]
tests/test_gelu.py ........                                                  [ 50%]
tests/test_isnan.py ........                                                 [ 58%]
tests/test_mm.py ..                                                          [ 60%]
tests/test_mul.py ........                                                   [ 68%]
tests/test_relu.py ........                                                  [ 76%]
tests/test_rsqrt.py ........                                                 [ 84%]
tests/test_sigmoid.py ........                                               [ 92%]
tests/test_sin.py ........                                                   [100%]

========================= 102 passed in 103.17s (0:01:43) ==========================

[voltjia]

pytest output:

============================= test session starts ==============================
platform linux -- Python 3.12.3, pytest-8.3.5, pluggy-1.5.0
rootdir: /home/voltjia/ntops
configfile: pyproject.toml
plugins: cov-6.0.0
collected 134 items

tests/test_abs.py ........                                               [  5%]
tests/test_add.py ........                                               [ 11%]
tests/test_addmm.py ..                                                   [ 13%]
tests/test_bmm.py ..                                                     [ 14%]
tests/test_cos.py ........                                               [ 20%]
tests/test_div.py ........                                               [ 26%]
tests/test_eq.py ........                                                [ 32%]
tests/test_exp.py ........                                               [ 38%]
tests/test_gelu.py ........                                              [ 44%]
tests/test_isinf.py ........                                             [ 50%]
tests/test_isnan.py ........                                             [ 56%]
tests/test_mm.py ..                                                      [ 58%]
tests/test_mul.py ........                                               [ 64%]
tests/test_ne.py ........                                                [ 70%]
tests/test_relu.py ........                                              [ 76%]
tests/test_rsqrt.py ........                                             [ 82%]
tests/test_sigmoid.py ........                                           [ 88%]
tests/test_sin.py ........                                               [ 94%]
tests/test_tanh.py ........                                              [100%]

======================= 134 passed in 490.19s (0:08:10) ========================