src/AbstractMessage.php
final public function has($fieldName)
    {
        if (!isset($this->data[$fieldName])) {
            return false;
        }

        if (is_array($this->data[$fieldName])) {
            return !empty($this->data[$fieldName]);
        }

        return true;
    }
final public function has($fieldName)
    {
        if (!isset($this->data[$fieldName])) {
            return false;
        }

        if (is_array($this->data[$fieldName])) {
            return !empty($this->data[$fieldName]);
        }

        return true;
    }
{@inheritdoc}