new (ActionMailer::Part)

    # File lib/action_mailer/part.rb, line 43
        def initialize(params)
          @content_type = params[:content_type]
          @content_disposition = params[:disposition] || "inline"
          @charset = params[:charset]
          @body = params[:body]
          @filename = params[:filename]
          @transfer_encoding = params[:transfer_encoding] || "quoted-printable"
          @headers = params[:headers] || {}
          @parts = []
        end