code: func EventFromChunk(sessionID string, chunk *SessionChunk) (EventFields, error) {
  	var fields EventFields
  	eventStart := time.Unix(0, chunk.Time).In(time.UTC).Round(time.Millisecond)
  	err := json.Unmarshal(chunk.Data, &fields)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	fields[SessionEventID] = sessionID
  	fields[EventIndex] = chunk.EventIndex
  	fields[EventTime] = eventStart
  	fields[EventType] = chunk.EventType
  	if fields[EventID] == "" {
  		fields[EventID] = uuid.New()
  	}
  	return fields, nil
  }
docs: // EventFromChunk returns event converted from session chunk