# File lib/faraday/request/multipart.rb, line 34
    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]['Content-Length'] = body.length.to_s
      return body
    end