private function uploadImage(string $purpose, string $imageData) : string
    {
        $parameters = [
            [
                'name' => 'purpose',
                'contents' => $purpose,
            ],
            [
                'name' => 'file',
                'filename' => 'dummy_file_name',
                'contents' => $imageData,
                'headers' => [
                    'Content-Type' => 'image/jpeg'
                ]
            ],
            [
                'name' => 'mimeType',
                'contents' => 'image/jpeg',
            ]
        ];

        $response = $this->postMultiPart(sprintf(self::SATCHEL_ENDPOINT, $this->id()), $parameters);

        return $response->url;
    }