    # 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