addresses = GMAIL.users().settings().sendAs().list( userId='me' ).execute().get('sendAs')
{ "sendAs": [{ "sendAsEmail": string, "displayName": string, "replyToAddress": string, "signature": string, "isPrimary": boolean, "isDefault": boolean, "treatAsAlias": boolean, "smtpMsa": { "host": string, "port": integer, "username": string, "password": string, "securityMode": string }, "verificationStatus": string }, ...] }
addresses = GMAIL.users().settings().sendAs().list( userId='me', fields='sendAs(sendAsEmail,isPrimary)' ).execute().get('sendAs')