* add get_subset method, add comment, rename variable
* add unit test
* Please mypy
* Fix as comment, support negative index, and fix index access error
* add and refine docstring, handle indices=0
* handle indices=0
* add empty list indices test
* rename in_meta in docstring and comments to in_metainfo
* clean meta nameing
* Fix negative indices error
* test empty list of get_subset
* fix comments and docstring
* add unit test
* Fix as comment
* Fix as comment
* add docstring to mention wrapped dataset should not inherit from Basedataset
* Fix wrapped dataset docstring
* Fix wrapped dataset docstring
* Fix method name, docstring, and comments
* Fix comments
* Fix comments
* Fix comments