code: def unary_trees():
      trees = tree_reader.read_trees(TREEBANK)
      trees = [t.prune_none().simplify_labels() for t in trees]
      assert len(trees) == len(TREES)
  
      return trees
  
imports: import itertools
  import pytest
  from stanza.models.constituency import parse_transitions
  from stanza.models.constituency import tree_reader
  from stanza.models.constituency.base_model import SimpleModel
  from stanza.models.constituency.in_order_oracle import *
  from stanza.models.constituency.parse_transitions import CloseConstituent, OpenConstituent, Shift, TransitionScheme
  from stanza.models.constituency.transition_sequence import build_treebank
  from stanza.tests import *
  from stanza.tests.constituency.test_transition_sequence import reconstruct_tree
label_desc: Use image node_id 2 for calling a global function with example usage: unary_trees() and returns: trees