curl --request POST \
  --url https://api.example.com/cancellable_synthesis \
  --header 'Content-Type: application/json' \
  --data '
{
  "accent_phrases": [
    {
      "moras": [
        {
          "text": "<string>",
          "vowel": "<string>",
          "vowel_length": 123,
          "pitch": 123,
          "consonant": "<string>",
          "consonant_length": 123
        }
      ],
      "accent": 123,
      "is_interrogative": false
    }
  ],
  "speedScale": 123,
  "pitchScale": 123,
  "intonationScale": 123,
  "volumeScale": 123,
  "prePhonemeLength": 123,
  "postPhonemeLength": 123,
  "outputSamplingRate": 123,
  "outputStereo": true,
  "pauseLength": 123,
  "pauseLengthScale": 1,
  "kana": "<string>"
}
'

"<string>"