    # File lib/chef/mixin/template.rb, line 72
            def source_listing
              @source_listing ||= begin
                line_index = line_number - 1
                beginning_line = line_index <= SOURCE_CONTEXT_WINDOW ? 0 : line_index - SOURCE_CONTEXT_WINDOW
                source_size = SOURCE_CONTEXT_WINDOW * 2 + 1
                lines = @template.split(/\n/)
                contextual_lines = lines[beginning_line, source_size]
                output = []
                contextual_lines.each_with_index do |line, index|
                  line_number = (index+beginning_line+1).to_s.rjust(3)
                  output << "#{line_number}: #{line}"
                end
                output.join("\n")
              end
            end