src/Smalot/Magento/Catalog/ProductAttributeSet.php
public function attributeAdd($attributeId, $attributeSetId, $attributeGroupId = null, $sortOrder = null)
    {
        return $this->__createAction('product_attribute_set.attributeAdd', func_get_args());
    }
public function attributeAdd($attributeId, $attributeSetId, $attributeGroupId = null, $sortOrder = null)
    {
        return $this->__createAction('product_attribute_set.attributeAdd', func_get_args());
    }
public function attributeAdd ( $ attributeId , $ attributeSetId , $ attributeGroupId = null , $ sortOrder = null ) { return $ this -> __createAction ( 'product_attribute_set.attributeAdd' , func_get_args ( ) ) ; }
Allows you to add an existing attribute to an attribute set.

@param string $attributeId
@param string $attributeSetId
@param string $attributeGroupId
@param string $sortOrder

@return ActionInterface
Allows you to add an existing attribute to an attribute set .