src/Bag/BagTrait.php
public function has($key)
    {
        return (isset($this->bag[$key]) || array_key_exists($key, $this->bag));
    }
public function has($key)
    {
        return (isset($this->bag[$key]) || array_key_exists($key, $this->bag));
    }
If bag container have given key.

@param  string|int
@return bool