docs: def merge(self, other, successor=None):
          """
          Merge two abstract states.
  
          For any node A whose dominance frontier that the current node (at the current program location) belongs to, we
          create a phi variable V' for each variable V that is defined in A, and then replace all existence of V with V'
          in the merged abstract state.
  
          :param VariableRecoveryState other: The other abstract state to merge.
          :return:                            The merged abstract state.
          :rtype:                             VariableRecoveryState
          """
  
          replacements = {}
          if successor in self.dominance_frontiers:
              replacements = self._make_phi_variables(successor, self, other)
  
          merged_stack_region = self.stack_region.copy().replace(replacements).merge(other.stack_region,
                                                                                     replacements=replacements)
          merged_register_region = self.register_region.copy().replace(replacements).merge(other.register_region,
                                                                                           replacements=replacements)
  
          state = VariableRecoveryFastState(
              successor,
              self._analysis,
              self.arch,
              self.function,
              stack_region=merged_stack_region,
              register_region=merged_register_region,
              processor_state=self.processor_state.copy().merge(other.processor_state),
          )
  
          return state