class Faraday::Request::Multipart

def create_multipart(env, params)
  boundary = env.request.boundary
  parts = process_params(params) do |key, value|
    Faraday::Parts::Part.new(boundary, key, value)
  end
  parts << Faraday::Parts::EpiloguePart.new(boundary)
  body = Faraday::CompositeReadIO.new(parts)
  env.request_headers[Faraday::Env::ContentLength] = body.length.to_s
  return body
end