code: def unary_model(pretrain_file):
      return build_model(
          pretrain_file, "--transition_scheme", "TOP_DOWN_UNARY"
      )
  
imports: import os
  import pytest
  import torch
  from stanza.models.common import pretrain
  from stanza.models.common.utils import set_random_seed
  from stanza.models.constituency import parse_transitions
  from stanza.tests import *
  from stanza.tests.constituency import test_parse_transitions
  from stanza.tests.constituency.test_trainer import build_trainer
label_desc: Use image node_id 3 for calling a global function with example usage: unary_model(pretrain_file) and returns: build_model