Syntax warning due to comparison of literals using is in Python 3.8

[tirkarthi]

find . -iname '*.py' | grep -Ev 'vendor|example|doc|tools|sphinx' | xargs -P4 -I{} python3.8 -Wall -m py_compile {}
./keras_resnet/benchmarks/__init__.py:74: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if benchmark is "MNIST":