* fix lint for graph_index.py
* pylint for base.py
* pylint for batched_graph.py
* pylint for frame.py; simplify and fix bugs in frame when index is slice type
* pylint for graph.py
* pylint for immutable_graph_index.py
* pylint for init.py
* pylint for rest files in root package
* pylint for _ffi package
* pylint for function package
* pylint for runtime package
* pylint for runtime.ir package
* add pylint to ci
* fix mx tests
* fix lint errors
* fix ci
* fix as requested
* fix lint
Minjie Wang