src/Models/ArrayableModel.php
public function offsetExists($offset)
    {
        return $this->getAccessor($offset) || $this->getAccessorForLanguageField($offset)
            ? true : isset($this->fields[$offset]);
    }
public function offsetExists($offset)
    {
        return $this->getAccessor($offset) || $this->getAccessorForLanguageField($offset)
            ? true : isset($this->fields[$offset]);
    }
Exists method for ArrayIterator.

@param $offset

@return bool