How to use the setupmeta.MetaDefs function in setupmeta

def test_meta_command_init():
    with pytest.raises(Exception):
        obj = setupmeta.MetaDefs()
        setupmeta.meta_command_init(obj, {})

def preprocess(self, upstream):
        self.find_project_dir(MetaDefs.dist_to_dict(upstream).pop("_setup_py_path", None))

        for require_field in ('install_requires', 'tests_require'):
            value = getattr(upstream, require_field)
            if isinstance(value, str if sys.version_info.major >= 3 else basestring) and value.startswith('@'):  # noqa: E501, F821 (basestring used by Python 2)
                self.add_definition(require_field, value, EXPLICIT)
                self.add_definition(require_field, requirements_from_file(value[1:]) or [], source=value[1:], override=True)

        if isinstance(upstream.extras_require, dict):
            if any([
                    isinstance(deps, str if sys.version_info.major >= 3 else basestring)  # noqa: F821 (basestring used by Python 2)
                    and deps.startswith('@')
                    for deps in upstream.extras_require.values()
            ]):
                self.add_definition('extras_require', upstream.extras_require, EXPLICIT)
                self.add_definition('extras_require', {
                    extra: (requirements_from_file(deps[1:]) or []) if isinstance(deps, str) and deps.startswith('@') else deps

def MetaCommand(cls):
    """Decorator allowing for less boilerplate in our commands"""
    return setupmeta.MetaDefs.register_command(cls)

def finalize(self, upstream):
        self.attrs.update(MetaDefs.dist_to_dict(upstream))

        self.find_project_dir(self.attrs.pop("_setup_py_path", None))
        scm = self.attrs.pop("scm", None)

        # Add definitions from setup()'s attrs (highest priority)
        for key, value in self.attrs.items():
            if key not in self.definitions:
                self.add_definition(key, value, EXPLICIT)

        # Add definitions from PKG-INFO, when available
        self.pkg_info = PackageInfo(MetaDefs.project_dir)
        for key, value in self.pkg_info.info.items():
            if key in MetaDefs.all_fields:
                self.add_definition(key, value, relative_path(self.pkg_info.path))

        # Allow to auto-fill 'name' from setup.py's __title__, if any
        self.merge(SimpleModule("setup.py"))
        title = self.definitions.get("title")
        if title:
            self.auto_fill("name", title.value, source=title.source)

        if "--name" in sys.argv[1:3]:
            # No need to waste time auto-filling anything if all we need to show is package name
            return self

        packages = self.attrs.get("packages", [])
        py_modules = self.attrs.get("py_modules", [])

        if not packages and not py_modules and self.name:

def show_expanded_python(self):
        """Copy-pastable setup.py, if one wants to get rid of setupmeta"""
        definitions = self.setupmeta.definitions
        print('"""\nGenerated by https://pypi.org/project/setupmeta/\n"""\n')
        print("from setuptools import setup\n\n")

        version = definitions.get("version")
        if version:
            print('__version__ = %s\n\n' % setupmeta.stringify(version.value, quote=True))

        print("setup(")

        defs = []
        for definition in sorted(definitions.values()):
            if not definition.value or definition.key not in setupmeta.MetaDefs.all_fields:
                continue

            if definition.key == "setup_requires":
                # When expanding, remove mention of 'setupmeta',
                # as expansion is aimed at giving a people a way to get a setup.py as-if setupmeta didn't exist
                # ie: it's a way of easily getting rid of setupmeta (should the need arise)
                if "setupmeta" in definition.value:
                    definition.value.remove("setupmeta")

                if definition.value:
                    definition.value = setupmeta.stringify(definition.value, quote=True, indent="        ")

            elif definition.key == "download_url":
                if version and version.value in definition.value:
                    definition.value = definition.value.replace(version.value, "%s")
                    definition.value = "%s %% __version__" % setupmeta.stringify(setupmeta.short(definition.value), quote=True)