code: def __get_file(self, file):
          
          file_object = None
          if file['name'] in request.files:
              file_object = request.files[file['name']]
              clean_filename = secure_filename(file_object.filename)
              if clean_filename == '':
                  return file_object
              if file_object and self.__allowed_extension(
                      clean_filename, file['extensions']):
                  return file_object
          elif file['name'] not in request.files and file['required']:
              return file_object
          return file_object
docs: Get request file and do a security check