maybe add some advanced duplicate removals

[jensbri]

Some background:

• in Option B, task concat a df the challenge was that I pressed the play button repeatedly and ended up adding (concat) to my df over and over again
• therefore, I wanted to check if I had done that programmatically: find duplicates; in other words: If there are 245 lines in the core dataset that is concat with 500 lines and I end up with 245+500+500 whereof 500 are 100% duplicates, that would be the main intended outcome
• what Ben mentioned in the first run was: removing duplicates from the tips by making sure that a subset of the columns is 100% match
• this is probably an important task for researchers dealing with imperfect data collection: Defining rules which columns NaN is still a valid row vs. not