def _build_multipart(cls, data):
        """
        Build up the MIME payload for the POST data
        """
        boundary = '--------------GHSKFJDLGDS7543FJKLFHRE75642756743254'
        sep_boundary = b'\n--' + boundary.encode('ascii')
        end_boundary = sep_boundary + b'--'
        end_items = (
            end_boundary,
            b"\n",
        )
        builder = functools.partial(
            cls._build_part,
            sep_boundary=sep_boundary,
        )
        part_groups = map(builder, data.items())
        parts = itertools.chain.from_iterable(part_groups)
        body_items = itertools.chain(parts, end_items)
        content_type = 'multipart/form-data; boundary=%s' % boundary
        return b''.join(body_items), content_type

        Build up the MIME payload for the POST data
        
product/gradle-plugin/src/main/python/setuptools/command/upload_docs.py