def attach(self,<EOL>filename=None,<EOL>content_type=None,<EOL>data=None,<EOL>disposition=None,<EOL>headers=None):
self.attachments.append(<EOL>Attachment(filename, content_type, data, disposition, headers))<EOL>
Adds an attachment to the message.

        :param filename: filename of attachment
        :param content_type: file mimetype
        :param data: the raw file data
        :param disposition: content-disposition (if any)