Level 2 optimization

[harrypuuter]

When i attempt a lvl 2 optimization, I get an error message

Traceback (most recent call last):
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/shapes/produce_shapes_tauID.py", line 1071, in <module>
    main(args)
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/shapes/produce_shapes_tauID.py", line 1036, in main
    g_manager.optimize(args.optimization_level)
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 116, in optimize
    self.optimize_selections()
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 140, in optimize_selections
    self._merge_children(merged_graph)
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 165, in _merge_children
    self._merge_children(child)
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 165, in _merge_children
    self._merge_children(child)
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 165, in _merge_children
    self._merge_children(child)
  [Previous line repeated 18 more times]
  File "/work/sbrommer/smhtt_ul/tauID/smhtt_ul/ntuple_processor/optimization.py", line 157, in _merge_children
    if child not in merged_children:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

unclear how this happens.