[Good first issue | Enhance] Add column description info in LLM prompt

[MooooCat]

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🚅Description

This GFI allows sdgx to obtain the column description from raw_data or raw_data sampled data, and return a string in a text form that LLM can understand. The information in the text should include but not be limited to:

• Column type: float type, int type, category type, datetime type, etc.;
• For numeric type columns: maximum value, minimum value, mean, standard deviation, distribution, etc.;
• For datetime type: start and end dates, datetime type format, etc.;
• For category types: specific category value, number of category values, etc.;
• For ID type: ID category, format, etc.;
• For other types of necessary information, developers are asked to add it based on their own creativity.

🏕Solution

Implements the _form_columns_description method of sdgx.models.LLM.single_table.base.LLMBaseModel.

synthetic-data-generator/sdgx/models/LLM/base.py

Line 89 in ec31560

def _form_columns_description(self):

This method returns a string.

Developers can refer to the implementation ideas of _form_message_with_offtable_features and _form_dataset_description methods.

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