useful resources
https://www.geeksforgeeks.org/adding-new-column-to-existing-dataframe-in-pandas/
https://www.geeksforgeeks.org/numpy-where-in-python/
https://stackoverflow.com/questions/36864690/iterate-through-a-dataframe-by-index
https://www.geeksforgeeks.org/python-pandas-melt/
https://twitter.com/dog_rates/status/670842764863651840
https://stackoverflow.com/questions/43093394/check-if-column-value-is-in-other-columns-in-pandas
https://nfpdiscussions.udacity.com/t/quality-or-tidiness-problem-question-2/41980/2