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

        $this->identity = $identity;

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

        $this->identity = $identity;

        return $this;
    }
Set identity

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