Patient IDs are actually review IDs?

Section `Time to slice and dice` in the Datasets chapter of the course discusses issues with the Drug Review Datasets mentions that the unnamed column might be a patient ID and tests that claim by showing that there are as many unique values as there are rows in the dataset. But that makes it more likely that the column is actually a review ID unique to each review (row), rather than patient ID as one patient might in theory review more than one drug.