このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
dynamodb could not unconvert attribute
対処
関連リンク
AWS DynamoDB: Could not unconvert attribute error - Stack Overflow
https://stackoverflow.com/questions/47926783/aws-dynamodb-could-not-unconvert-attribute-error
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