GitLab

Make computation more efficient by generating the NodeSet based on a
single dict comprehension instead of repeatedly calling the union
method.
Signed-off-by: Jonas Mårtensson <jonas.martensson@ri.se>

Computation is significantly faster if the path is stored as an object
attribute the first time it is generated and just returned from this
attribute for subsequent calls.

See https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation

The documentation is now generated automatically for each tag
via GitLab CI.

Install importlib-metadata in CI (missing dependency for pip-tools: https://github.com/jazzband/pip-tools/issues/1352)