code: function wrapCallback(api, span, done) {
    var fn = function(err, res) {
      if (api.enhancedDatabaseReportingEnabled()) {
        if (err) {
          // Errors may contain sensitive query parameters.
          span.addLabel('mongoError', err);
        }
        if (res) {
          var result = res.result ? res.result : res;
          span.addLabel('result', result);
        }
      }
      span.endSpan();
      if (done) {
        done(err, res);
      }
    };
    return api.wrap(fn);
  }
docs: Wraps the provided callback so that the provided span will
  be closed immediately after the callback is invoked.
  
  @param {Span} span The span to be closed.
  @param {Function} done The callback to be wrapped.
  @return {Function} The wrapped function.