Need a custom graph parser for Gephi

[oyeb]

Gephi allows multiple attributes for each vertex, and this can be interpreted as a dictionary of keys mapping to values.
Our graph creates many "keys" whose values are lists-of-values, or put simply, we have attributes that are multi-valued (so we need a dictionary whose elements can be lists too).
Currently, the neither the GephiStreamer API nor Gephi directly support multi-valued attributes. So we'll have to definitely improve GephiStreamer API to parse such dictionaries, and might also have tinker with Gephi's internal vertex representation.