'Encode a GNTP Notification Message
@return: GNTP Notification Message ready to be sent'

def encode(self):

    self.validate()
    SEP = u':    '
    EOL = u'\r\n'
    message = (self.format_info() + EOL)
    for (k, v) in self.headers.iteritems():
        message += (((k + SEP) + unicode(v)) + EOL)
    message += EOL
    return message.encode('utf-8')
