def convert_value(value, source_currency, target_currency):
<EOL>if source_currency == target_currency:<EOL><INDENT>return value<EOL><DEDENT>rate = get_rate(source_currency, target_currency)<EOL>return value * rate<EOL>
Converts the price of a currency to another one using exchange rates

    :param price: the price value
    :param type: decimal

    :param source_currency: source ISO-4217 currency code
    :param type: str

    :param target_currency: target ISO-4217 currency code
    :param type: str

    :returns: converted price instance
    :rtype: ``Price``