def print_env(k, v)
      if v
        puts @shell_printer.export(k, v)
      else
        puts @shell_printer.unset(k)
      end
    end
def print_env(k, v)
      if v
        puts @shell_printer.export(k, v)
      else
        puts @shell_printer.unset(k)
      end
    end
Print an export or unset statement suitable for user's shell