Fix Literals, improve performance

What's Changed

• Fix AttributeError in field_parsing.py by @lebrice in #251
• Add lru_cache wrapper in docstring parsing by @lebrice in #252
• added example for how to use the flag helper by @LTluttmann in #256
• Lazy import of numpy/torch etc. by @breuleux in #253
• Fix literals for Python 3.9 by @brentyi in #260
• Add test to reproduce #259 by @lebrice in #262
• upgrade precommit hooks by @lebrice in #263

New Contributors

• @LTluttmann made their first contribution in #256
• @breuleux made their first contribution in #253
• @brentyi made their first contribution in #260

Full Changelog: v0.1.2...v0.1.3