How to use the setupmeta.warn function in setupmeta

def _show_dependencies(definitions):
    """
    Conveniently  get dependency tree via ./setup.py check --dep, similar to https://pypi.org/project/pipdeptree
    """
    if setupmeta.pkg_resources is None or not hasattr(setupmeta.pkg_resources, "WorkingSet"):
        setupmeta.warn("pkg_resources is not available, can't show dependencies")
        return 1

    venv = find_venv()
    if not venv:
        setupmeta.warn("Could not find virtual environment to scan for dependencies")
        return 1

    entries = list(find_subfolders(venv, ["site-packages"]))
    if not entries:
        setupmeta.warn("Could not find 'site-packages' subfolder in '%s'" % venv)
        return 1

    tree = DepTree(setupmeta.pkg_resources.WorkingSet(entries), definitions)
    print(tree.rendered())
    return len(tree.conflicts) + len(tree.cycles)

if self.strategy:
                setupmeta.warn(self.problem)

            setupmeta.trace("not auto-filling version due to problem: [%s]" % self.problem)
            return

        gv = self.scm.get_version()
        if self.generate_version_file:
            path = setupmeta.project_path(setupmeta.VERSION_FILE)
            with open(path, "w") as fh:
                fh.write("%s" % gv)

        if gv.patch and "patch" not in self.strategy.bumpable:
            msg = "patch version component should be .0 for versioning strategy '%s', " % self.strategy
            msg += "'.%s' from current version tag '%s' will be ignored" % (gv.patch, gv)
            setupmeta.warn(msg)

        rendered = self.strategy.rendered(gv)
        if cv and gv:
            cvc = setupmeta.version_components(cv)
            cvv = Version(main="%s.%s.%s" % cvc[:3], distance=cvc[4], commitid=gv.commitid, dirty=cvc[5])
            actual = self.strategy.rendered(cvv, auto_bumped=False)
            cleaned = self.strategy.rendered(gv.non_dirty)
            if actual not in (cleaned, rendered):
                source = vdef.sources[0].source
                expected = self.strategy.rendered(gv, extra=False)
                msg = "In %s version should be '%s', not '%s'" % (source, expected, cv)
                setupmeta.warn(msg)

        self.meta.auto_fill("version", rendered, self.scm.name, override=True)

def __init__(self, main, extra, separator, branches, hook, **kwargs):
        self.main = main
        self.extra = extra
        if kwargs:
            setupmeta.warn("Ignored fields for 'versioning': %s" % kwargs)

        self.main_bits = self.bits(main)
        if isinstance(self.main_bits, list):
            self.bumpable = [b.text for b in self.main_bits if b.text in BUMPABLE]

        else:
            self.bumpable = []

        self.extra_bits = self.bits(extra)
        self.separator = separator
        self.branches = branches
        self.hook = hook
        if self.branches and hasattr(self.branches, "lstrip"):
            self.branches = self.branches.lstrip("(").rstrip(")")

        self.branches = setupmeta.listify(self.branches, separator=",")

def _show_dependencies(definitions):
    """
    Conveniently  get dependency tree via ./setup.py check --dep, similar to https://pypi.org/project/pipdeptree
    """
    if setupmeta.pkg_resources is None or not hasattr(setupmeta.pkg_resources, "WorkingSet"):
        setupmeta.warn("pkg_resources is not available, can't show dependencies")
        return 1

    venv = find_venv()
    if not venv:
        setupmeta.warn("Could not find virtual environment to scan for dependencies")
        return 1

    entries = list(find_subfolders(venv, ["site-packages"]))
    if not entries:
        setupmeta.warn("Could not find 'site-packages' subfolder in '%s'" % venv)
        return 1

    tree = DepTree(setupmeta.pkg_resources.WorkingSet(entries), definitions)
    print(tree.rendered())
    return len(tree.conflicts) + len(tree.cycles)

if package and "." not in package:
                # Look at top level modules only
                self.merge(
                    SimpleModule(package, "__about__.py"),
                    SimpleModule(package, "__version__.py"),
                    SimpleModule(package, "__init__.py"),
                    SimpleModule("src", package, "__about__.py"),
                    SimpleModule("src", package, "__version__.py"),
                    SimpleModule("src", package, "__init__.py"),
                )

        if not self.name:
            warn("'name' not specified in setup.py, auto-fill will be incomplete")

        elif not self.definitions.get("packages") and not self.definitions.get("py_modules"):
            warn("No 'packages' or 'py_modules' defined, this is an empty python package")

        scm = scm or project_scm(MetaDefs.project_dir)
        self.versioning = Versioning(self, scm)
        self.versioning.auto_fill_version()

        self.fill_urls()

        self.auto_adjust("author", self.extract_email)
        self.auto_adjust("contact", self.extract_email)
        self.auto_adjust("maintainer", self.extract_email)

        self.requirements = Requirements(self.pkg_info)
        self.auto_fill_requires("install_requires")
        self.auto_fill_requires("tests_require")
        if self.requirements.dependency_links:
            self.auto_fill("dependency_links", self.requirements.dependency_links, self.requirements.links_source)

if not self.enabled:
            setupmeta.trace("not auto-filling version, versioning is disabled")
            return

        vdef = self.meta.definitions.get("version")
        if vdef and vdef.source and vdef.source.lower().endswith("-info"):
            # We already got version from PKG-INFO
            return

        cv = vdef.sources[0].value if vdef and vdef.sources else None
        if self.problem:
            if not cv:
                self.meta.auto_fill("version", "0.0.0", "missing")

            if self.strategy:
                setupmeta.warn(self.problem)

            setupmeta.trace("not auto-filling version due to problem: [%s]" % self.problem)
            return

        gv = self.scm.get_version()
        if self.generate_version_file:
            path = setupmeta.project_path(setupmeta.VERSION_FILE)
            with open(path, "w") as fh:
                fh.write("%s" % gv)

        if gv.patch and "patch" not in self.strategy.bumpable:
            msg = "patch version component should be .0 for versioning strategy '%s', " % self.strategy
            msg += "'.%s' from current version tag '%s' will be ignored" % (gv.patch, gv)
            setupmeta.warn(msg)

        rendered = self.strategy.rendered(gv)

return parse_requirements, PipSession

    except ImportError:
        pass

    try:
        # pip < 10.0
        from pip.req import parse_requirements
        from pip.download import PipSession

        return parse_requirements, PipSession

    except ImportError:
        from setupmeta import warn

        warn("Can't find PipSession, won't auto-fill requirements")
        return None, None