src/Collection/Traits/ArrayAccessTrait.php
public function offsetGet($offset)
    {
        if (!$this->offsetExists($offset)) {
            throw new \InvalidArgumentException(
                sprintf('Offset %s does not exist in collection', $offset)
            );
        }

        return $this->elements[$offset];
    }
public function offsetGet($offset)
    {
        if (!$this->offsetExists($offset)) {
            throw new \InvalidArgumentException(
                sprintf('Offset %s does not exist in collection', $offset)
            );
        }

        return $this->elements[$offset];
    }
Return collection element at $offset

@return mixed