human
I wrote the below code

    if (boundary is None):
        boundary = ('---------------WerkzeugFormPart_%s%s' % (time(), random()))
    _closure = [BytesIO(), 0, False]
    if use_tempfile:
        def write_binary(string):
            (stream, total_length, on_disk) = _closure
            if on_disk:
                stream.write(string)
            else:
                length = len(string)
                if ((length + _closure[1]) <= threshold):
                    stream.write(string)
                else:
                    new_stream = TemporaryFile('wb+')
                    new_stream.write(stream.getvalue())
                    new_stream.write(string)
                    _closure[0] = new_stream
                    _closure[2] = True
                _closure[1] = (total_length + length)
    else:
        write_binary = _closure[0].write
    def write(string):
        write_binary(string.encode(charset))
    if (not isinstance(values, MultiDict)):
        values = MultiDict(values)
    for (key, values) in iterlists(values):
        for value in values:
            write(('--%s\r\nContent-Disposition:    form-data.
   name="%s"' % (boundary, key)))
            reader = getattr(value, 'read', None)
            if (reader is not None):
                filename = getattr(value, 'filename', getattr(value, 'name', None))
                content_type = getattr(value, 'content_type', None)
                if (content_type is None):
                    content_type = ((filename and mimetypes.guess_type(filename)[0]) or 'application/octet-stream')
                if (filename is not None):
                    write(('.
   filename="%s"\r\n' % filename))
                else:
                    write('\r\n')
                write(('Content-Type:    %s\r\n\r\n' % content_type))
                while 1:
                    chunk = reader(16384)
                    if (not chunk):
                        break
                    write_binary(chunk)
            else:
                if (not isinstance(value, string_types)):
          ...

What's a good function header?

=====
Here's a good function header?
assistant
#Here's a good function header.

def stream_encode_multipart(values, use_tempfile=True, threshold=(1024 * 500), boundary=None, charset='utf-8'):