func (mt mimeType) IsVideo() bool {
	return strings.HasPrefix(string(mt), "video/") || mt == "application/vnd.rn-realmedia-vbr"
}
IsVideo returns true for video MIME-types
package dms
import (
	"log"
	"mime"
	"net/http"
	"os"
	"path"
	"strings"
)
func init() {
	if err := mime.AddExtensionType(".rmvb", "application/vnd.rn-realmedia-vbr"); err != nil {
		log.Printf("Could not register application/vnd.rn-realmedia-vbr MIME type: %s", err)
	}
	if err := mime.AddExtensionType(".ogv", "video/ogg"); err != nil {
		log.Printf("Could not register video/ogg MIME type: %s", err)
	}
	if err := mime.AddExtensionType(".ogg", "audio/ogg"); err != nil {
		log.Printf("Could not register audio/ogg MIME type: %s", err)
	}
}
type mimeType string
func (mt mimeType) IsMedia() bool {
	return mt.IsVideo() || mt.IsAudio() || mt.IsImage()
}