Fix missing type annotations

[jettify]

Fixes #163

[codecov]

Codecov Report

Merging #164 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #164   +/-   ##
=======================================
  Coverage   85.67%   85.67%           
=======================================
  Files           4        4           
  Lines         370      370           
  Branches       47       47           
=======================================
  Hits          317      317           
  Misses         40       40           
  Partials       13       13

Impacted Files	Coverage Δ
aiomonitor/monitor.py	83.03% <100%> (ø)	⬆️
aiomonitor/utils.py	93.02% <100%> (ø)	⬆️

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