Multipart allow us to set file content type like:
`--9544b22b7836f99902cf668b2307d779
Content-Disposition: form-data; name="file1_name"; filename="file1_name.png"
Content-Type: image/bmp

file1_data
--9544b22b7836f99902cf668b2307d779--`

but this library dosnt have any interface to get this content type header: Content-Type: image/bmp.
Could you fix it?