docs: def _get_symbol_index(stroke_id_needle, segmentation):
      """
      Parameters
      ----------
      stroke_id_needle : int
          Identifier for the stroke of which the symbol should get found.
      segmentation : list of lists of integers
          An ordered segmentation of strokes to symbols.
  
      Returns
      -------
      The symbol index in which stroke_id_needle occurs
  
      Examples
      --------
      >>> _get_symbol_index(3, [[0, 1, 2], [3, 4, 5], [6, 7]])
      1
      >>> _get_symbol_index(6, [[0, 1, 2], [3, 4, 5], [6, 7]])
      2
      >>> _get_symbol_index(7, [[0, 1, 2], [3, 4, 5], [6, 7]])
      2
      """
      for symbol_index, symbol in enumerate(segmentation):
          if stroke_id_needle in symbol:
              return symbol_index
      return None