class_docstr: A class to maintain the state during planarity check.
class_docstr_tok: ["A","class","to","maintain","the","state","during","planarity","check","."]
docstr: Recursive version of :meth:`sign`.
docstr_tok: ["Recursive","version","of",":","meth",":","`","sign","`","."]
code: def sign_recursive(self, e):
      """Recursive version of :meth:`sign`."""
      if self.ref[e] is not None:
          self.side[e] = self.side[e] * self.sign_recursive(self.ref[e])
          self.ref[e] = None
      return self.side[e]
  
imports: from collections import defaultdict
  import networkx
label_desc: Use image node_id 13 for calling the LRPlanarity obj's underlying member method code with example usage: obj.sign_recursive(e) and returns: self