def write io_path_or_writer
      if io_path_or_writer.is_a? Writer
        io_path_or_writer.write self
      else
        writer(io_path_or_writer).write(self)
      end
    end
def write io_path_or_writer
      if io_path_or_writer.is_a? Writer
        io_path_or_writer.write self
      else
        writer(io_path_or_writer).write(self)
      end
    end
Write this Workbook to a File, IO Stream or Writer Object. The latter will
 make more sense once there are more than just an Excel-Writer available.