docstr: Number of visited nodes is the max number among outputs plus 1 (the next operation). 
docstr_tok: ["Number","of","visited","nodes","is","the","max","number","among","outputs","plus","1","(","the","next","operation",")","."]
code: def calculate_dataflow_len(self) -> int:
      """Number of visited nodes is the max number among outputs plus 1 (the next operation)."""
      return 1 + max(
          output.supplementary_data.data_flow_length
          for output in self.outputs
      )
  
file_path: FEDOT/fedot/core/data/merge/supplementary_data_merger.py
imports: from typing import Dict, List
  import numpy
  from golem.core.log import default_log
  from fedot.core.data.data import OutputData
  from fedot.core.data.supplementary_data import SupplementaryData
  from fedot.core.repository.dataset_types import DataTypesEnum
  from fedot.preprocessing.data_types import TableTypesCorrector
label_desc: Use image node_id 3 for calling the SupplementaryDataMerger obj's underlying member method code with example usage: obj.calculate_dataflow_len() and returns: unknown