Traits/Document/Attributable.php
public function setAttributeInGroup($group, $key, $value)
    {
        $this->attributes[$group][$key] = $value;

        return $this;
    }
public function setAttributeInGroup($group, $key, $value)
    {
        $this->attributes[$group][$key] = $value;

        return $this;
    }
Set attributes by group and key

@param string $group
@param string $key
@param array $attributes

@return self