docs: def convert_value(value, source_currency, target_currency):
      """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``
  
      """
      # If price currency and target currency is same
      # return given currency as is
      if source_currency == target_currency:
          return value
  
      rate = get_rate(source_currency, target_currency)
  
      return value * rate