code: def _at_variables(self, calculator, rule, scope, block):
          
          warn_deprecated(
              rule,
              "@variables and @vars are deprecated.  "
              "Just assign variables at top-level.")
          _rule = rule.copy()
          _rule.unparsed_contents = block.unparsed_contents
          _rule.namespace = rule.namespace
          _rule.properties = []
          self.manage_children(_rule, scope)
docs: Implements @variables and @vars