code: def operator(self, node, children):
          'operator = "+" / "-" / "*" / "/"'
          operators = {'+': op.add, '-': op.sub, '*': op.mul, '/': op.div}
          return operators[node.textf operator(self, node, children):
          'operator = "+" / "-" / "*" / "/"'
          operators = {'+': op.add, '-': op.sub, '*': op.mul, '/': op.div}
          return operators[node.text]
docs: operator = "+" / "-" / "*" / "/"