code: def _attempt_proof(self, clauses):
      # map indices to lists of indices, to store attempted unifications
      tried = defaultdict(list)
  
      i = 0
      while i < len(clauses):
          if not clauses[i].is_tautology():
              # since we try clauses in order, we should start after the last
              # index tried
              if tried[i]:
                  j = tried[i][-1] + 1
              else:
                  j = (
                      i + 1
                  )  # nothing tried yet for 'i', so start with the next
  
              while j < len(clauses):
                  # don't: 1) unify a clause with itself,
                  #       2) use tautologies
                  if i != j and j and not clauses[j].is_tautology():
                      tried[i].append(j)
                      newclauses = clauses[i].unify(clauses[j])
                      if newclauses:
                          for newclause in newclauses:
                              newclause._parents = (i + 1, j + 1)
                              clauses.append(newclause)
                              if not len(
                                  newclause
                              ):  # if there's an empty clause
                                  return (True, clauses)
                          i = (
                              -1
                          )  # since we added a new clause, restart from the top
                          break
                  j += 1
          i += 1
      return (False, clauses)
  
imports: import operator
  from collections import defaultdict
  from functools import reduce
  from nltk.inference.api import BaseProverCommand, Prover
  from nltk.sem import skolemize
  from nltk.sem.logic import AndExpression, ApplicationExpression, EqualityExpression, Expression, IndividualVariableExpression, NegatedExpression, OrExpression, Variable, VariableExpression, is_indvar, unique_variable
label_desc: Use image node_id 2 for calling the ResolutionProver obj's underlying member method code with example usage: obj._attempt_proof(clauses) and returns: False,  clauses, True,  clauses