public function attr($name, $discriminatorValue = null)
    {
        if (empty($name)) {
            throw new \InvalidArgumentException;
        }

        return new Operand\Attribute($this, $name, $discriminatorValue);
    }
public function attr($name, $discriminatorValue = null)
    {
        if (empty($name)) {
            throw new \InvalidArgumentException;
        }

        return new Operand\Attribute($this, $name, $discriminatorValue);
    }
public function attr ( $ name , $ discriminatorValue = null ) { if ( empty ( $ name ) ) { throw new \ InvalidArgumentException ; } return new Operand \ Attribute ( $ this , $ name , $ discriminatorValue ) ; }
Return an attribute object, used for building an expression.

@see QueryBuilder::attr()

@param string      $name Top-level attribute name.
@param string|null $discriminatorValue

@return Operand\Attribute|Operand\RootAttribute
Return an attribute object used for building an expression .