def METHOD_NAME(self, basepaths, folder_name):
    maps = [{}]  # the first dict will be used for added/modified entries
    for basepath in basepaths:
        data = {}
        path = os.path.join(basepath, folder_name)
        if os.path.exists(path):
            for key in os.listdir(path):
                with open(os.path.join(path, key), 'r') as h:
                    data[key] = yaml.safe_load(h)
        maps.append(data)
    return ChainMap(*maps)