src/Metable/AttributeBag.php
public function forget($key)
    {
        if ($attribute = $this->get($key)) {
            $attribute->setValue(null);
        }

        return $this;
    }
public function forget($key)
    {
        if ($attribute = $this->get($key)) {
            $attribute->setValue(null);
        }

        return $this;
    }
Unset attribute.

@param  string $key
@return $this