import hashlib


def get_nccl_store_name(group_name):
    """Generate the unique name for the NCCLUniqueID store (named actor).

    Args:
        group_name (str): unique user name for the store.
    Return:
        str: MD5-hexlified name for the store.
    """
    if not group_name:
        raise ValueError("group_name is None.")
    hexlified_name = hashlib.md5(group_name.encode()).hexdigest()
    return hexlified_name