POSTMAN - Post Request Error {Document not found}

Problem statement is when we are sending the post request in using postman we are getting error message as below 

{"error":{"errorCode":"DATABASE_ERROR","message":"Error: Message: {\"Errors\":[\"Encountered exception while executing function. Exception = Error: Document not found.

the problem here is we are sending this post request with payload as "Text"  as shown below.

• Now to solve the issue we just have to select Json instead of Text and you will get the success response.