In this exercise, you will create a function that takes two currency codes and converts them to a ticker suitable for downloading from yfinance.

code: The currency ISO code $($e$.$g$.,$ USD $=$ US Dollar, AUD $=$ Australian Dollar$).$ You can find a list of currency codes here.

fx: The exchange rate, i$.$e$.$ the value of one currency in terms of another currency. We will represent an exchange rate like this:

AUD$/$USD : The price in US dollars of one Australian dollar

USD$/$AUD : The price in Australian dollars of one US dollar

AAA$/$BBB : The price in currency BBB of one unit of currency AAA

from$\_$cur: The currency which we want to price $($AAA in the example above$)$

to$\_$cur: The price of one unit of the from$\_$cur $($BBB in the example above$)$

Yahoo finance uses the following naming rules to define the ticker of the exchange rate AAA$/$BBB $($the price of one unit of AAA in terms of currency BBB$)$:

$1.$ If AAA is the USD, then the ticker is $"$BBB$=$X$",$ i$.$e$.,$ the second currency code with $"=$X$"$ added at the end.

$2.$ If AAA is not the USD, then the ticker is "AAABBB$=$X$"$

For example, the ticker for AUD$/$USD is "AUDUSD$=$X$",$ while the ticker for USD$/$AUD is "AUD$=$X$"$

The scaffold provides you with a declaration defining the function's arguments and a docstring that describes what the function should do$.$ You need to fill in the body of the function. Note that a function called get$\_$fx is provided as a reference. Once your fx$\_$code function passes the diagnostic tests, you should be able to copy the entire file to an environment with yfinance installed $($e$.$g$.,$ PyCharm$)$ and use this program to download currency data.