balance_etypes in partition_grap_lp

Hello, in `partition_graph_lp.py` script, there is an argument `--balance-train`, which is used to decide whether to create the `balance_etypes` variable. However, `balance_etypes` is not used anywhere after it is created. Are there any plans to support balancing edge types in heterogeneous graphs?

Regards,
Kacper

Start with partition_graph_lp.py, focusing on --balance-train and the creation of balance_etypes, then trace whether edge-type balancing is represented elsewhere. Done requires a decided scope for heterogeneous-edge-type balancing and an agreed implementation or documented answer; the issue names no test.

Written by the indexing model from the issue text.