Adding Attachment to Mail using Send Mail API V2.1in Zoho CRM

I am trying to create a custom function where it sends a template email using the Send Mail API for version 2.1. In the structure, I would like to add an attachment which is available inside the record.

In API 2.1, one can add in attachment by providing the attachment id which I got via using Get Attachment list invoke url method to gain the specific file id. However, it resulted an error as below:

{"data":[{"code":"INVALID_DATA","details":{"api_name":"id","json_path":"$.data[0].attachments[0].id"},"message":"There is no file exists with the given id","status":"error"}]}

the method i was trying was :

//getting list of attachment

getAttachments = invokeurl

[

url :"https://www.zohoapis.com/crm/v2.1/Contacts/" + ContactID + "/Attachments"

type :GET

connection:"zcrm"

];

attachment_id = getAttachments.get("data").get(0).get("$file_id");

//inputting inside email

Attach = List();

attach = Map();

attach.put("id",attachment_id.toString());

Attach.add(attach);

mergedatalist = List();

mergedata = Map();

mergedata.put("from",frm);

//sender

mergedata.put("to",toward);

//recipient

mergedata.put("org_email",false);

mergedata.put("attachments",Attach);

//attachment id

mergedata.put("template",temp);

//template id

mergedatalist.add(mergedata);

data = Map();

data.put("data",mergedatalist);

//send email

sendingmail = invokeurl

[

url :"https://www.zohoapis.com/crm/v2.1/Contacts/" + ContactID + "/actions/send_mail"

type :POST

parameters:data.toString()

connection:"zcrm"

];

info sendingmail;