<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_settings(instance=None):
 """Pick correct settings instance and set it to a global variable."""


    global settings

    settings = None

    if instance:
        settings = import_settings(instance)

    elif "INSTANCE_FOR_DYNACONF" in os.environ:
        settings = import_settings(os.environ["INSTANCE_FOR_DYNACONF"])

    elif "FLASK_APP" in os.environ:  # pragma: no cover
        with suppress(ImportError, click.UsageError):
            from flask.cli import ScriptInfo

            flask_app = ScriptInfo().load_app()
            settings = flask_app.config
            click.echo(
                click.style(
                    "Flask app detected", fg="white", bg="bright_black"
                )
            )

    elif "DJANGO_SETTINGS_MODULE" in os.environ:  # pragma: no cover
        sys.path.insert(0, os.path.abspath(os.getcwd()))
        try:
            # Django extension v2
            from django.conf import settings

            settings.DYNACONF.configure()
        except (ImportError, AttributeError):
            # Backwards compatible with old django extension (pre 2.0.0)
            import dynaconf.contrib.django_dynaconf  # noqa
            from django.conf import settings as django_settings

            django_settings.configure()
            settings = django_settings

        if settings is not None:
            click.echo(
                click.style(
                    "Django app detected", fg="white", bg="bright_black"
                )
            )

    if settings is None:
        settings = LazySettings()