client.transformations.schedules.delete(id=[1,2,3], external_id="3")

List<Item> deleteSchedule = List.of(Item.newBuilder()   
          .setExternalId("10")   
          .build());
Boolean isUnSchedule =   
          client.transformations().schedules().unSchedule(deleteSchedule);

curl --request POST \
  --url https://{cluster}.cognitedata.com/api/v1/projects/{project}/transformations/schedules/delete \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "items": [
    {
      "externalId": "my.known.id"
    }
  ],
  "ignoreUnknownIds": true
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({items: [{externalId: 'my.known.id'}], ignoreUnknownIds: true})
};

fetch('https://{cluster}.cognitedata.com/api/v1/projects/{project}/transformations/schedules/delete', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://{cluster}.cognitedata.com/api/v1/projects/{project}/transformations/schedules/delete",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'items' => [
        [
                'externalId' => 'my.known.id'
        ]
    ],
    'ignoreUnknownIds' => true
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://{cluster}.cognitedata.com/api/v1/projects/{project}/transformations/schedules/delete"

	payload := strings.NewReader("{\n  \"items\": [\n    {\n      \"externalId\": \"my.known.id\"\n    }\n  ],\n  \"ignoreUnknownIds\": true\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://{cluster}.cognitedata.com/api/v1/projects/{project}/transformations/schedules/delete")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"items\": [\n    {\n      \"externalId\": \"my.known.id\"\n    }\n  ],\n  \"ignoreUnknownIds\": true\n}"

response = http.request(request)
puts response.read_body

{}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "missing": [
      {
        "externalId": "my.known.id"
      }
    ],
    "duplicated": [
      {
        "externalId": "my.known.id"
      }
    ]
  }
}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "missing": [
      {
        "externalId": "my.known.id"
      }
    ],
    "duplicated": [
      {
        "externalId": "my.known.id"
      }
    ]
  }
}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "missing": [
      {
        "externalId": "my.known.id"
      }
    ],
    "duplicated": [
      {
        "externalId": "my.known.id"
      }
    ]
  }
}