class_docstr: Implementation of VF2 algorithm for matching directed graphs.
  
  Suitable for DiGraph and MultiDiGraph instances.
class_docstr_tok: ["Implementation","of","VF2","algorithm","for","matching","directed","graphs",".","Suitable","for","DiGraph","and","MultiDiGraph","instances","."]
docstr: Reinitializes the state of the algorithm.
  
  This method should be redefined if using something other than DiGMState.
  If only subclassing GraphMatcher, a redefinition is not necessary.
docstr_tok: ["Reinitializes","the","state","of","the","algorithm",".","This","method","should","be","redefined","if","using","something","other","than","DiGMState",".","If","only","subclassing","GraphMatcher",",","a","redefinition","is","not","necessary","."]
code: def initialize(self):
      """Reinitializes the state of the algorithm.
  
      This method should be redefined if using something other than DiGMState.
      If only subclassing GraphMatcher, a redefinition is not necessary.
      """
  
      # core_1[n] contains the index of the node paired with n, which is m,
      #           provided n is in the mapping.
      # core_2[m] contains the index of the node paired with m, which is n,
      #           provided m is in the mapping.
      self.core_1 = {}
      self.core_2 = {}
  
      # See the paper for definitions of M_x and T_x^{y}
  
      # in_1[n]  is non-zero if n is in M_1 or in T_1^{in}
      # out_1[n] is non-zero if n is in M_1 or in T_1^{out}
      #
      # in_2[m]  is non-zero if m is in M_2 or in T_2^{in}
      # out_2[m] is non-zero if m is in M_2 or in T_2^{out}
      #
      # The value stored is the depth of the search tree when the node became
      # part of the corresponding set.
      self.in_1 = {}
      self.in_2 = {}
      self.out_1 = {}
      self.out_2 = {}
  
      self.state = DiGMState(self)
  
      # Provide a convenient way to access the isomorphism mapping.
      self.mapping = self.core_1.copy()
  
imports: import sys
label_desc: Use image node_id 3 for calling the DiGraphMatcher obj's underlying member method code with example usage: obj.initialize() without return types