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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _find_folders(self, folder_name):
 """Return a list of sub-directories."""

        found_folders = []
        for app_config in apps.get_app_configs():
            folder_path = os.path.join(app_config.path, folder_name)
            if os.path.isdir(folder_path):
                found_folders.append(folder_path)
        return found_folders