use "encode/base64"
class val MIMEContent
var transfer_type: MIMETransferType val
var content_type: MIMEContentType val
var raw_data: (String val | Array[U8] val) = ""
new val create(content_type': MIMEContentType val, transfer_type': MIMETransferType val, raw_data': (String val | Array[U8] val)) =>
content_type = content_type'
transfer_type = transfer_type'
raw_data = raw_data'
fun render(): String =>
transfer_type.content_transfer_encoding_header() +
content_type.content_type() +
content_type.content_disposition() +
"Mime-Version: 1.0\r\n\r\n" +
transfer_type.encode(raw_data) + "\r\n"