There is a minor error in the instructions of the given assignment.
The given instructions are:
2. Add a legend to the graph using
plt.legend(). Use any labels you find suitable.
The answer appears to only accept labels as defined in the answer code.
For example, if you were to label the UK graph as “The United Kingdom” (as opposed to “The UK”) and submit your answer, the message “Your 1st plot doesn’t match what we expected.” appears.