code: def _get_file_stream(self, total_content_length, content_type, filename=None,
                          content_length=None):
          
          return default_stream_factory(total_content_length, content_type,
                                        filename, content_length)
docs: Called to get a stream for the file upload.
  
          This must provide a file-like class with `read()`, `readline()`
          and `seek()` methods that is both writeable and readable.
  
          The default implementation returns a temporary file if the total
          content length is higher than 500KB.  Because many browsers do not
          provide a content length for the files only the total content
          length matters.
  
          :param total_content_length: the total content length of all the
                                       data in the request combined.  This value
                                       is guaranteed to be there.
          :param content_type: the mimetype of the uploaded file.
          :param filename: the filename of the uploaded file.  May be `None`.
          :param content_length: the length of this file.  This value is usually
                                 not provided because webbrowsers do not provide
                                 this value.