def file_created_date
      assert_exists
      web_response = @object.getWebResponse(true)
      Time.parse(web_response.getResponseHeaderValue("Last-Modified").to_s)
    end
def file_created_date
      assert_exists
      web_response = @object.getWebResponse(true)
      Time.parse(web_response.getResponseHeaderValue("Last-Modified").to_s)
    end
returns the file created date of the image