src/Model/Attribute/Accessor/Assignee.php
public function setAssignee(?string $assignee)
    {
        if (null !== $assignee) {
            if (!preg_match('/^[a-z]+$/i', $assignee)) {
                throw new DomainException('Assignee is not valid.');
            }
        }

        $this->assignee = $assignee;

        return $this;
    }
public function setAssignee(?string $assignee)
    {
        if (null !== $assignee) {
            if (!preg_match('/^[a-z]+$/i', $assignee)) {
                throw new DomainException('Assignee is not valid.');
            }
        }

        $this->assignee = $assignee;

        return $this;
    }
Set assignee

@param string $assignee
@return object
@throws \DomainException