code: def create(self, key, value):
          
          data = values.of({'Key': key, 'Value': value, })
  
          payload = self._version.create(
              'POST',
              self._uri,
              data=data,
          )
  
          return VariableInstance(
              self._version,
              payload,
              service_sid=self._solution['service_sid'],
              environment_sid=self._solution['environment_sid'],
          )
docs: Create a new VariableInstance
  
          :param unicode key: The key
          :param unicode value: The value
  
          :returns: Newly created VariableInstance
          :rtype: twilio.rest.serverless.v1.service.environment.variable.VariableInstance