code: function resolveEventConfig(ringpop, traceEvent) {
      var tracerConfig = tracerConfigMap[traceEvent];
      if (!tracerConfig) {
          return null;
      }
      var sourcePath = tracerConfig.sourcePath;
  
      // subtle but important -- if we resolve here, then the underlying object
      // can never change. if we do latent resolution, there may be a resource
      // leak when we try to remove listener from something that is out of our
      // reachable scope.
      var emitter = getIn(ringpop, sourcePath.slice(0, -1));
      var event = _.last(sourcePath);
  
      return emitter && _.defaults(
          {},
          {
              sourceEmitter: emitter,
              sourceEvent: event,
              traceEvent: traceEvent
          },
          tracerConfig
      );
  }
docs: resolves and returns a tracer config object, with traceEvent, sourceEmitter, and sourceEvent bound