all occurrences should be higher then aliens occurrences
The issue #22 (closed) describes the problem.
The fix is to use pd.isna()
instead of not
to properly
map ecoregion to species observed by obis.
I have also added the test based on code form issue #22 (closed)
hm = marinvaders.Species(145634) set(hm.all_occurrences.ECO_CODE).symmetric_difference(set(hm.reported_as_alien.ECO_CODE))