code: func NewExporter(opts ...Option) (*Exporter, error) {
  	c := defaultConfig()
  	for _, opt := range opts {
  		opt(c)
  	}
  
  	tracer := lightstep.NewTracer(c.tracerOptions)
  	if tracer == nil {
  		if err := c.tracerOptions.Validate(); err != nil {
  			return nil, err
  		}
  		return nil, ErrFailedToCreateExporter
  	}
  
  	return &Exporter{
  		tracer: tracer,
  	}, nil
  }
docs: // NewExporter creates a new Exporter.
  // It returns an error if the underlying tracer could not be created, e.g., due to invalid options