Fixes for python 3.9, postponed type annotations

[lebrice]

What's Changed

• Fix issue 62 by @lebrice in Fix issue 62 #99
• Replace yaml.full_load with yaml.safe_load by @lebrice in Replace yaml.full_load with yaml.safe_load #109
• Add python 3.9 support, fix future annotations by @lebrice in Add python 3.9 support, fix future annotations #110

Full Changelog: v0.0.18...v0.0.19

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This discussion was created from the release Fixes for python 3.9, postponed type annotations.