message: Expose modular file system header in pip install package
  This PR tries to expose modular file system header in pip install package
  so that downstream packages could use the header files with pip install
diff: @@ -36,6 +36,7 @@ transitive_hdrs(
  "//tensorflow/cc/saved_model:loader",
  "//tensorflow/cc/saved_model:reader",
  "//tensorflow/cc/saved_model:bundle_v2",
  + "//tensorflow/c/experimental/filesystem:modular_filesystem",
  # WARNING: None of the C/C++ code under python/ has any API guarantees, and TF team
  # reserves the right to change APIs and other header-level interfaces. If your custom
  # op uses these headers, it may break when users upgrade their version of tensorflow.
  