support sorting by multiple columns

[joocer]

No description provided.

[Copilot]

Pull Request Overview

This PR removes unused imports across multiple test files and code modules, while also making minor code formatting improvements to adhere to style guidelines.

• Removed numerous unused imports from test files and modules
• Fixed f-string usage by removing unnecessary f-prefixes where string interpolation wasn't used
• Updated version number from 0.6.27 to 0.6.28
• Improved code formatting and line wrapping for better readability

Reviewed Changes

Copilot reviewed 57 out of 57 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/*	Removed unused imports across multiple test files
mabel/version.py	Updated version number to 0.6.28
mabel/utils/*	Improved code formatting and removed unnecessary f-strings
mabel/data/*	Enhanced code formatting and readability
mabel/adapters/*	Code style improvements and formatting
examples/Reading Data.ipynb	Removed unused Reader import
Makefile	Updated build configuration with better formatting

Comments suppressed due to low confidence (1)

mabel/data/writers/writer.py:1

• Similar to the previous issue, these InvalidDataSetError exceptions are created but not raised. They should be prefixed with raise to actually throw the exceptions.

import datetime

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[Copilot]

The InvalidDataSetError exception is created but not raised. This should be raise InvalidDataSetError(...) to actually throw the exception.

[Copilot]

Use is not None instead of != None for None comparisons to follow Python best practices.

Suggested change

	type(val).__name__ for val in top.collect_list(key) if val != None
	type(val).__name__ for val in top.collect_list(key) if val is not None

[Copilot]

The item.get(column) call is duplicated for each item. Consider storing the result in a variable to avoid the double lookup: value = item.get(column); if value is not None.

Suggested change

	values = [
	item.get(column) for item in items if item.get(column) is not None
	]
	values = []
	for item in items:
	value = item.get(column)
	if value is not None:
	values.append(value)