whole_func_string: function listIndexes(callback) {
              debug('[%s] list existing indexes', self.queueName);
              collection.indexInformation({full: true}, function(err, indexInfo) {
                if (err) {
                  debug('[%s] error getting indexInfo. skipping ttl index check: %s', self.queueName, err);
                  return callback(null, null);
                }
                return callback(null, indexInfo);
              });
            }
func_code_string: function listIndexes(callback) {
              debug('[%s] list existing indexes', self.queueName);
              collection.indexInformation({full: true}, function(err, indexInfo) {
                if (err) {
                  debug('[%s] error getting indexInfo. skipping ttl index check: %s', self.queueName, err);
                  return callback(null, null);
                }
                return callback(null, indexInfo);
              });
            }
func_documentation_string: Check if there's already a TTL index for the 'deleted' field. If there is, and the TTL value is different, delete it so it can be recreated by the mongodb-queue module