code: func SampleCollectorToProto(c *SampleCollector) *tipb.SampleCollector {
  	collector := &tipb.SampleCollector{
  		NullCount: c.NullCount,
  		Count:     c.Count,
  		FmSketch:  FMSketchToProto(c.FMSketch),
  		TotalSize: &c.TotalSize,
  	}
  	if c.CMSketch != nil {
  		collector.CmSketch = CMSketchToProto(c.CMSketch)
  	}
  	for _, item := range c.Samples {
  		collector.Samples = append(collector.Samples, item.Value.GetBytes())
  	}
  	return collector
  }
docs: // SampleCollectorToProto converts SampleCollector to its protobuf representation.