add require once

[Assimilationstheorie]

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[codecov[bot]]

Codecov Report

Merging #136 into master will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #136   +/-   ##
=========================================
  Coverage     87.23%   87.23%           
  Complexity     1041     1041           
=========================================
  Files            59       59           
  Lines          3534     3534           
=========================================
  Hits           3083     3083           
  Misses          451      451

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[ottlinger]

Thanks for your contribution.