src/Primitive/Container/Container.php
public function numericKeys()
    {
        $keys = new static;

        foreach ($this->items as $key => $value)
        {
            if (is_numeric($key)) $keys->set($key, $value);
        }

        return $keys;
    }
public function numericKeys()
    {
        $keys = new static;

        foreach ($this->items as $key => $value)
        {
            if (is_numeric($key)) $keys->set($key, $value);
        }

        return $keys;
    }
Return items only with numeric keys.

@return static