Add exception for CSV without headers.

[philschmid]

What does this PR do?

This PR adds an exception when a CSV is sent without or with the wrong headers. Since it is not guaranteed to parse the CSV correctly. see #24

Explanation:

When using batch_transform sagemaker is sending exactly 1 row as input to the endpoint, e.g.

united thx off the response, finally got through the 45 min wait and talked to someone.

The issue with this is that the csv.sniffer would identify the , as delimiter and would split this into two columns, and create an input for question-answering instead of text-classification. There is no way to identify wether the input is 1 column based or 2 column based just from 1 input, e.g. question-answering input

the flight was delayed 45 minutes, How long was the flight delayed?

When someone would use MultiRecord instead the sniffer would identify the delimiter correctly, but for me these are too many constraints and if for it to work properly.

Tested with

where do i live?,My Name is Philipp and I live in Nuremberg.
What is the capital?,Berlin is the capital of Germany.

got as response

{
  "code": 400,
  "type": "InternalServerException",
  "message": "You need to provide the correct CSV with Header columns to use it with the inference toolkit default handler. : 400"
}

Also added a unit test for it.