# File lib/chef/mixin/params_validate.rb, line 79
      def set_or_return(symbol, arg, validation)
        iv_symbol = "@#{symbol.to_s}".to_sym
        map = {
          symbol => validation
        }

        if arg == nil && self.instance_variable_defined?(iv_symbol) == true
          self.instance_variable_get(iv_symbol)
        else
          opts = validate({ symbol => arg }, { symbol => validation })
          self.instance_variable_set(iv_symbol, opts[symbol])
        end
      end