Unpropriate condition.

Hello. I confirm that everything in the task works well. Mostly I really love conditions. They look wise. But not here fully. The last condition is interwoven with the third.

• If the final marker comes before the initial marker, then return an empty string.

with

• If there is no final marker, the last character should be considered the ending of a string.

I deem that if the end marker is before the start marker that marker is considered simple text. It is like HTML highlighting in the IDE.

Afterward, the code does not look optimized.