code: def get_unique_combinations(combinations_per_row):
      """Performs set.union on a list of sets
  
      Parameters
      ----------
  
      combinations_per_row : List[Set[Tuple[int]]]
          list of combination assignments per row
  
      Returns
      -------
      Set[Tuple[int]]
          all unique label combinations
      """
      return set.union(*combinations_per_row)
  
file_path: scikit-multilearn/skmultilearn/model_selection/measures.py
imports: import numpy
  import itertools
label_desc: Use image node_id 4 for calling a global function with example usage: get_unique_combinations(combinations_per_row) and returns: set