src/LightSaml/Model/Metadata/IdpSsoDescriptor.php
public function addAttribute(Attribute $attribute)
    {
        if (false == is_array($this->attributes)) {
            $this->attributes = array();
        }
        $this->attributes[] = $attribute;

        return $this;
    }
public function addAttribute(Attribute $attribute)
    {
        if (false == is_array($this->attributes)) {
            $this->attributes = array();
        }
        $this->attributes[] = $attribute;

        return $this;
    }
@param \LightSaml\Model\Assertion\Attribute $attribute

@return IdpSsoDescriptor