# File lib/prawn/layout/grid.rb, line 39
      def initialize(pdf, options = {})
        valid_options = [:columns, :rows, :gutter, :row_gutter, :column_gutter]
        Prawn.verify_options valid_options, options
      
        @pdf = pdf
        @columns = options[:columns]
        @rows = options[:rows]
        set_gutter(options)
      end