Add fix for checking `is_time_series()` property based on `data_type` attr

[tomvothecoder]

Description

• Closes #877

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules

If applicable:

• [ ] New and existing unit tests pass with my changes (locally and CI/CD build)
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[tomvothecoder]

@chengzhuzhang This PR should fix the attribute error (tested with your run script). You can rebase your eamxx_1024 branch on the latest cdat-migration-fy24

EDIT: Actually let me address a few more of the open issues in #871 first so you don't have to keep rebasing.

[chengzhuzhang]

@tomvothecoder thank you. I will keep modifying eamxx_1024, the changes are mostly contained within variable derivation, so it is easy to rebase.