def download_input
      return unless input_is_url?
      Dir.chdir(@work_directory) do
        @input_path = File.join(@work_directory, safe_filename(@input))
        @file_name = File.basename(@input_path, File.extname(@input_path))
        download(@input, @input_path)
      end
    end
def download_input
      return unless input_is_url?
      Dir.chdir(@work_directory) do
        @input_path = File.join(@work_directory, safe_filename(@input))
        @file_name = File.basename(@input_path, File.extname(@input_path))
        download(@input, @input_path)
      end
    end
If the input is a URL, download the file before beginning processing.