Fix type errors

[mhidas]

Fixes #117

[codecov]

Codecov Report

Merging #151 (7cdd401) into master (f4dca31) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #151      +/-   ##
==========================================
+ Coverage   70.44%   70.46%   +0.02%     
==========================================
  Files          12       12              
  Lines        1130     1131       +1     
  Branches      151      152       +1     
==========================================
+ Hits          796      797       +1     
  Misses        317      317              
  Partials       17       17              

Impacted Files	Coverage Δ
...tools/timeseries_products/aggregated_timeseries.py	95.15% <100.00%> (-0.15%)	⬇️
aodntools/timeseries_products/common.py	88.73% <100.00%> (+2.29%)	⬆️
aodntools/timeseries_products/hourly_timeseries.py	98.17% <100.00%> (-0.05%)	⬇️

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[mhidas]

@evacougnon @leonardolaiolo I've tagged you both as reviewers, but only really need one. To be discussed with @ggalibert who will have time for this next iteration (or later...)