code: def test_initial_unary(model=None):
      # it doesn't make sense to start with a CompoundUnary
      if model is None:
          model = SimpleModel()
  
      state = build_initial_state(model)[0]
      unary = parse_transitions.CompoundUnary("ROOT", "VP")
      assert unary.label == (
          "ROOT",
          "VP",
      )
      assert not unary.is_legal(state, model)
      unary = parse_transitions.CompoundUnary("VP")
      assert unary.label == ("VP",)
      assert not unary.is_legal(state, model)
  
imports: import pytest
  from stanza.models.constituency import parse_transitions
  from stanza.models.constituency.base_model import SimpleModel, UNARY_LIMIT
  from stanza.models.constituency.parse_transitions import TransitionScheme, Shift, CloseConstituent, OpenConstituent
  from stanza.tests import *
label_desc: Use image node_id 4 for calling a global function with example usage: test_initial_unary(model) without return types