src/AbstractMessage.php
final public function addToList($fieldName, array $values)
    {
        $this->guardFrozenMessage();
        $field = static::schema()->getField($fieldName);
        Assertion::true($field->isAList(), sprintf('Field [%s] must be a list.', $fieldName), $fieldName);

        foreach ($values as $value) {
            $field->guardValue($value);
            $this->data[$fieldName][] = $value;
        }

        unset($this->clearedFields[$fieldName]);
        return $this;
    }
final public function addToList($fieldName, array $values)
    {
        $this->guardFrozenMessage();
        $field = static::schema()->getField($fieldName);
        Assertion::true($field->isAList(), sprintf('Field [%s] must be a list.', $fieldName), $fieldName);

        foreach ($values as $value) {
            $field->guardValue($value);
            $this->data[$fieldName][] = $value;
        }

        unset($this->clearedFields[$fieldName]);
        return $this;
    }
{@inheritdoc}
@return static