For each include line referencing a _py39 file or directory in docs_src, replace
    the _py39 label with _py310.
    """
    include_pattern = re.compile(r"\{[^}]*docs_src/[^}]*_py39[^}]*\.py[^}]*\}")
    count = 0
    for md_file in sorted(en_docs_path.rglob("*.md")):
        content = md_file.read_text(encoding="utf-8")
        if "_py39" not in content:

#   value in the "env_vars" list that you can choose to copy that environment.
#      Ex. 1: TFCI=py311,linux_x86_cuda,nightly_upload  (nightly job)
#      Ex. 2: TFCI=py39,linux_x86,rbe                   (continuous job)
#   Non-Googlers should replace "nightly_upload" or "rbe" with
#   "public_cache,disk_cache".
#   Googlers should replace "nightly_upload" with "public_cache,disk_cache" or