Import and export formats for graph data

[makkus]

This topic serves as a place to suggest, record and discuss possible options for import-/ and export-data-formats for graph data.

The following list will be updated along the way:

• csv file(s): one (required) file with edges data, one (optional) file with node attribute data
• graphml
• gefx
• json (might require different output profiles)

Relevant links:

• open issue: create graph from file (other than CSV) #4
• https://networkx.org/documentation/stable/reference/readwrite/json_graph.html