class_docstr: Active and inactive nodes in a level.
class_docstr_tok: ["Active","and","inactive","nodes","in","a","level","."]
code: def __init__(self):
      self.active = set()
      self.inactive = set()
  
file_path: networkx/networkx/algorithms/flow/utils.py
imports: from collections import deque
  import networkx
label_desc: Use image node_id 1 to create a new Level object  with example: obj = Level()