class_docstr: Sorting network class.
  
  From Wikipedia : A sorting network is an abstract mathematical model
  of a network of wires and comparator modules that is used to sort a
  sequence of numbers. Each comparator connects two wires and sort the
  values by outputting the smaller value to one wire, and a larger
  value to the other.
docstr: Return the number of comparison-swap used.
docstr_tok: ["Return","the","number","of","comparison-swap","used","."]
code: def length(self):
      """Return the number of comparison-swap used."""
      return sum(len(level) for level in self)
  
file_path: deap/doc/code/tutorials/part_4/sortingnetwork.py
label_desc: Use image node_id 7 for calling the SortingNetwork obj's underlying member method code with example usage: obj.length() and returns: sum