source concepts documentation

docs/api/cpp_std.md

docs/api/generator.md

docs/api/index.md

docs/api/source_objects.md

docs/api/tree.md

docs/usage/generator_scripts.md

mkdocs.yml

src/pystencilssfg/composer/basic_composer.py

src/pystencilssfg/configuration.py

src/pystencilssfg/generator.py

src/pystencilssfg/source_concepts/source_objects.py

src/pystencilssfg/tree/__init__.py

src/pystencilssfg/tree/basic_nodes.py