def add_attachment(self, filename, open_file):
fields = {<EOL>'<STR_LIT>': self.client.api_key,<EOL>'<STR_LIT>': self.client.user_auth_token<EOL>}<EOL>content_type, body = self.encode_multipart_formdata(<EOL>fields=fields,<EOL>filename=filename,<EOL>file_values=open_file<EOL>)<EOL>return self.fetch_json(<EOL>uri_path=self.base_uri + '<STR_LIT>',<EOL>http_method='<STR_LIT:POST>',<EOL>body=body,<EOL>headers={'<STR_LIT:Content-Type>': content_type},<EOL>)<EOL>
Adds an attachment to this card.