You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: gen_property_activitystreams_startTime.go
    path of file: ./repos/gotosocial/vendor/github.com/superseriousbusiness/activity/streams/impl/activitystreams/property_starttime
    
    the code of the file until where you have to start completion: // Code generated by astool. DO NOT EDIT.

package propertystarttime

import (
	"fmt"
	datetime "github.com/superseriousbusiness/activity/streams/values/dateTime
    
func (this ActivityStreamsStartTimeProperty) Serialize() (interface{}, error) {
	if this.IsXMLSchemaDateTime() {
		return datetime.SerializeDateTime(this.Get())
	} else if this.IsIRI() {
		return this.iri.String(), nil
	}
	return this.unknown, nil
}