fix(imports): remove invalid lines when parsing notebooks

[mkniewallner]

Resolves #653.

PR Checklist

• A description of the changes is added to the description of this PR.
• If there is a related issue, make sure it is linked to this PR.
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

Description of changes

Avoid parsing magics in notebooks, as they are not valid Python but notebook-specifics. Also fixes an issue with continuation characters that comes from the fact that we don't strip \n suffixes in notebook source code, which also caused the location reporters to show the wrong line location.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.8%. Comparing base (5494d09) to head (ef7f1c9).

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #656   +/-   ##
=====================================
  Coverage   91.8%   91.8%           
=====================================
  Files         34      34           
  Lines        947     947           
  Branches     197     197           
=====================================
  Hits         870     870           
  Misses        60      60           
  Partials      17      17           

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