public function listGetConfig($definition = null)
    {
        if (!$definition) {
            $definition = $this->primaryDefinition;
        }

        if (!$config = array_get($this->listConfig, $definition)) {
            $config = $this->listConfig[$definition] = $this->makeConfig($this->listDefinitions[$definition], $this->requiredConfig);
        }

        return $config;
    }