Support for storing str type data

[Chaoyingz]

🌟 Feature Description

Support for storing str type data.

Motivation

1. Application scenario
2. Related works (Papers, Github repos etc.):
3. Any other relevant and important information:

Store data such as name, industry, and block of stocks.

Alternatives

This data is a bit like the category type in the pandas library, we can store the string in a list and then store its index.

Additional Notes