Resolve "In GraphGroup, store node/edge selection information as graph attribute"

With this MR, information about the node/edge data selection in GraphGroup.create_graph is stored as (networkx) graph attribute.

Details

The node/edge data is selected via .sel or .isel. The coordinates of the data after selection (which are still available in the DataArray) are stored as graph attribute (dictionary of coord-values keyed by dimension).

Anything to double-check?

Should the selection information of node/edge property data also be stored (i.e. in GraphGroup.set_<node/edge>_property)? ✅

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped
  • Reviewed & approved by @

Related issues

Closes #228 (closed)