addS3file (s3file: S3File, url: string, data:string): Observable<S3File> {
return this.http.post<S3File>(url, s3file, httpOptions).pipe(
  tap((s3file: S3File) => this.log(`added s3file w/ id=${s3file.id}`)),
  catchError(this.handleError<S3File>('adds3file'))
);
  }

file_path = 'screen.png'
with open(file_path, 'rb') as data:
    files = {'file': data}
    url = post_data['url']
    request_data = post_data['fields']

    r = requests.post(url, data=request_data, files=files)