code: def test_node_str():
      # given
      operation_type = "logit"
      test_model_node = PipelineNode(operation_type=operation_type)
      expected_node_description = operation_type
  
      # when
      actual_node_description = str(test_model_node)
  
      # then
      assert actual_node_description == expected_node_description
  
imports: import numpy
  import pytest
  from golem.core.dag.linked_graph_node import LinkedGraphNode
  from sklearn.datasets import load_iris
  from sklearn.linear_model import LogisticRegression
  from sklearn.metrics import accuracy_score, classification_report
  from fedot.core.data.data import InputData
  from fedot.core.data.data_split import train_test_data_setup
  from fedot.core.operations.model import Model
  from fedot.core.pipelines.node import PipelineNode
  from fedot.core.repository.dataset_types import DataTypesEnum
  from fedot.core.repository.tasks import Task, TaskTypesEnum
  from fedot.core.utils import DEFAULT_PARAMS_STUB, NESTED_PARAMS_LABEL
label_desc: Use image node_id 5 for calling a global function with example usage: test_node_str() without return types