Performance improvement

[t-takuho]

Performance improvements:

• Replace the existing variable check with in expression.
• Replace the formula dependency chain with a set.

英語に自信がないので、日本語でも記載します。。。
パフォーマンスの改善：

• 変数の存在チェックをin句で置換
• 数式の依存関係チェーンをSetで置換

[rangermeier]

This PR removes the usage of eval().
This is not just a performance improvement but also removes a potential security issue.