Add notes that version is generated during install (pytorch#386)

Author: scotts

setup.py

@@ -196,6 +196,7 @@ def _write_version_files():
             print("INFO: Didn't find sha. Is this a git repo?")
 
     with open(_ROOT_DIR / "src/torchcodec/version.py", "w") as f:
+        f.write("# Note that this file is generated during install.\n")
         f.write(f"__version__ = '{version}'\n")
 
 

src/torchcodec/__init__.py

@@ -10,6 +10,7 @@
 from . import decoders, samplers  # noqa
 
 try:
+    # Note that version.py is generated during install.
     from .version import __version__  # noqa: F401
 except Exception:
     pass