How to use the s3contents._version.NotThisMethod function in s3contents

def git_versions_from_keywords(keywords, tag_prefix, verbose):
    """Get version information from git keywords."""
    if not keywords:
        raise NotThisMethod("no keywords at all, weird")
    refnames = keywords["refnames"].strip()
    if refnames.startswith("$Format"):
        if verbose:
            print("keywords are unexpanded, not using")
        raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
    refs = set([r.strip() for r in refnames.strip("()").split(",")])
    # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
    # just "foo-1.0". If we see a "tag: " prefix, prefer those.
    TAG = "tag: "
    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
    if not tags:
        # Either we're using git < 1.8.3, or there really are no tags. We use
        # a heuristic: assume all version tags have a digit. The old git %d
        # expansion behaves like git log --decorate=short and strips out the
        # refs/heads/ and refs/tags/ prefixes that would let us distinguish
        # between branches and tags. By ignoring refnames without digits, we

def git_versions_from_keywords(keywords, tag_prefix, verbose):
    """Get version information from git keywords."""
    if not keywords:
        raise NotThisMethod("no keywords at all, weird")
    refnames = keywords["refnames"].strip()
    if refnames.startswith("$Format"):
        if verbose:
            print("keywords are unexpanded, not using")
        raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
    refs = set([r.strip() for r in refnames.strip("()").split(",")])
    # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
    # just "foo-1.0". If we see a "tag: " prefix, prefer those.
    TAG = "tag: "
    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
    if not tags:
        # Either we're using git < 1.8.3, or there really are no tags. We use
        # a heuristic: assume all version tags have a digit. The old git %d
        # expansion behaves like git log --decorate=short and strips out the
        # refs/heads/ and refs/tags/ prefixes that would let us distinguish
        # between branches and tags. By ignoring refnames without digits, we
        # filter out many common branch names like "release" and
        # "stabilization", as well as "HEAD" and "master".
        tags = set([r for r in refs if re.search(r'\d', r)])
        if verbose:
            print("discarding '%s', no digits" % ",".join(refs - tags))

def get_versions():
    """Get version information or return default if unable to do so."""
    # I am in _version.py, which lives at ROOT/VERSIONFILE_SOURCE. If we have
    # __file__, we can work backwards from there to the root. Some
    # py2exe/bbfreeze/non-CPython implementations don't do __file__, in which
    # case we can only use expanded keywords.

    cfg = get_config()
    verbose = cfg.verbose

    try:
        return git_versions_from_keywords(get_keywords(), cfg.tag_prefix, verbose)
    except NotThisMethod:
        pass

    try:
        root = os.path.realpath(__file__)
        # versionfile_source is the relative path from the top of the source
        # tree (where the .git directory might live) to this file. Invert
        # this to find the root from __file__.
        for i in cfg.versionfile_source.split('/'):
            root = os.path.dirname(root)
    except NameError:
        return {
            "version": "0+unknown",
            "full-revisionid": None,
            "dirty": None,
            "error": "unable to find root of source tree"
        }

if verbose:
            print("no .git in %s" % root)
        raise NotThisMethod("no .git directory")

    GITS = ["git"]
    if sys.platform == "win32":
        GITS = ["git.cmd", "git.exe"]
    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
    # if there isn't one, this yields HEX[-dirty] (no NUM)
    describe_out = run_command(
        GITS,
        ["describe", "--tags", "--dirty", "--always", "--long", "--match", "%s*" % tag_prefix],
        cwd=root)
    # --long was added in git-1.5.5
    if describe_out is None:
        raise NotThisMethod("'git describe' failed")
    describe_out = describe_out.strip()
    full_out = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
    if full_out is None:
        raise NotThisMethod("'git rev-parse' failed")
    full_out = full_out.strip()

    pieces = {}
    pieces["long"] = full_out
    pieces["short"] = full_out[:7]    # maybe improved later
    pieces["error"] = None

    # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
    # TAG might have hyphens.
    git_describe = describe_out

    # look for -dirty suffix

GITS = ["git"]
    if sys.platform == "win32":
        GITS = ["git.cmd", "git.exe"]
    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
    # if there isn't one, this yields HEX[-dirty] (no NUM)
    describe_out = run_command(
        GITS,
        ["describe", "--tags", "--dirty", "--always", "--long", "--match", "%s*" % tag_prefix],
        cwd=root)
    # --long was added in git-1.5.5
    if describe_out is None:
        raise NotThisMethod("'git describe' failed")
    describe_out = describe_out.strip()
    full_out = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
    if full_out is None:
        raise NotThisMethod("'git rev-parse' failed")
    full_out = full_out.strip()

    pieces = {}
    pieces["long"] = full_out
    pieces["short"] = full_out[:7]    # maybe improved later
    pieces["error"] = None

    # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
    # TAG might have hyphens.
    git_describe = describe_out

    # look for -dirty suffix
    dirty = git_describe.endswith("-dirty")
    pieces["dirty"] = dirty
    if dirty:
        git_describe = git_describe[:git_describe.rindex("-dirty")]

def versions_from_parentdir(parentdir_prefix, root, verbose):
    """Try to determine the version from the parent directory name.

    Source tarballs conventionally unpack into a directory that includes
    both the project name and a version string.
    """
    dirname = os.path.basename(root)
    if not dirname.startswith(parentdir_prefix):
        if verbose:
            print("guessing rootdir is '%s', but '%s' doesn't start with "
                  "prefix '%s'" % (root, dirname, parentdir_prefix))
        raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
    return {
        "version": dirname[len(parentdir_prefix):],
        "full-revisionid": None,
        "dirty": False,
        "error": None
    }