def METHOD_NAME(self, coin_type, delta=0):
    if coin_type not in COIN_TYPES:
        raise ValueError("coin_type must be in ('pp', 'gp', 'ep', 'sp', 'cp')")
    delta_out = ""
    if delta:
        delta_out = f" ({delta:+,})"
    coin_value = f"{getattr(self, coin_type):,}"
    return f"{COIN_TYPES[coin_type]['icon']} {coin_value} {coin_type}{delta_out}"