code: def update(self, key=values.unset, value=values.unset):
          
          return self._proxy.update(key=key, value=value, )
docs: Update the VariableInstance
  
          :param unicode key: The key
          :param unicode value: The value
  
          :returns: Updated VariableInstance
          :rtype: twilio.rest.serverless.v1.service.environment.variable.VariableInstance