How to use the watchgod.watcher.Change function in watchgod

def _walk(self, dir_path, changes, new_files):
        for entry in os.scandir(dir_path):
            if entry.is_dir():
                if self.should_watch_dir(entry):
                    self._walk(entry.path, changes, new_files)
            elif self.should_watch_file(entry):
                mtime = entry.stat().st_mtime
                new_files[entry.path] = mtime
                old_mtime = self.files.get(entry.path)
                if not old_mtime:
                    changes.add((Change.added, entry.path))
                elif old_mtime != mtime:
                    changes.add((Change.modified, entry.path))

def check(self):
        changes = set()
        new_files = {}
        try:
            self._walk(str(self.root_path), changes, new_files)
        except OSError as e:
            # happens when a directory has been deleted between checks
            logger.warning('error walking file system: %s %s', e.__class__.__name__, e)

        # look for deleted
        deleted = self.files.keys() - new_files.keys()
        if deleted:
            changes |= {(Change.deleted, entry) for entry in deleted}

        self.files = new_files
        return changes

def _walk(self, dir_path, changes, new_files):
        for entry in os.scandir(dir_path):
            if entry.is_dir():
                if self.should_watch_dir(entry):
                    self._walk(entry.path, changes, new_files)
            elif self.should_watch_file(entry):
                mtime = entry.stat().st_mtime
                new_files[entry.path] = mtime
                old_mtime = self.files.get(entry.path)
                if not old_mtime:
                    changes.add((Change.added, entry.path))
                elif old_mtime != mtime:
                    changes.add((Change.modified, entry.path))