code: def test_calculate_data_flow_len_correct():
      """Function checks whether the number of nodes visited by the data block
      is calculated correctly"""
  
      # Pipeline consists of 3 nodes
      simple_pipeline = generate_straight_pipeline()
      data = get_synthetic_regression_data(n_samples=100, n_features=2)
  
      simple_pipeline.fit(data)
      predict_output = simple_pipeline.predict(data)
  
      assert predict_output.supplementary_data.data_flow_length == 2
  
file_path: FEDOT/test/unit/data/test_supplementary_data.py
imports: import numpy
  import pytest
  from fedot.core.data.data import OutputData
  from fedot.core.data.merge.data_merger import DataMerger
  from fedot.core.data.merge.supplementary_data_merger import SupplementaryDataMerger
  from fedot.core.data.supplementary_data import SupplementaryData
  from fedot.core.pipelines.node import PipelineNode
  from fedot.core.pipelines.pipeline import Pipeline
  from fedot.core.repository.dataset_types import DataTypesEnum
  from fedot.core.repository.tasks import Task, TaskTypesEnum
  from fedot.preprocessing.data_types import TYPE_TO_ID
  from test.unit.data.test_data_merge import unequal_outputs_table
  from test.unit.tasks.test_regression import get_synthetic_regression_data
label_desc: Use image node_id 4 for calling a global function with example usage: test_calculate_data_flow_len_correct() without return types