'554, b'Transaction failed: Nested group in sending email using Amazon Aws SES

I want to send email from my Ubuntu server thru Amazon AWS SES. I've a working code and it's able to send an email.

However when I wrap the working code within a function it's giving this error:

Something with SMTP went wrong...
(554, b'Transaction failed: Nested group')

I'm attaching visual code comparison, .. I'm curious as to what could be wrong.

python-3.x amazon-ses

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