'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.'

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)
