Graph-analytics returns edges for non existing nodes

[Stafeeva]

Describe the bug

When fetching graph-analytics, we are getting nodes and edges, but there are edges for non existing nodes like ‘Agent’, so the graph cannot be constructed.

API calls (requests/responses)
Example, GET https://dev.nexus.ocp.bbp.epfl.ch/v1/graph-analytics/copies/sscx/relationships

Screenshots
Notice, there is no node 'Agent', but we are getting an edge with the target 'Agent'

Additional context
Add any other context about the problem here.