Merge recent changes from the original repo

[wehs7661]

Description

Here we merge recent changes from the original repo to this fork.

Type of Change

• Bug fix
• New feature
• Documentation update
• Unit test and CI update

Checklist

Starting from PR wehs7661#62, external PRs must keep the following checklist in the PR.

• I have read the contributing guidelines.
• My code follows the project’s coding style and is free from linting errors examined by flake8.
• My code comes with docstrings that follow the NumPy docstrings standard.
• I have updated the documentation in the docs directory if my changes affect the project's functionality or usage.
• I have added new tests for new features or changes to existing features. The code coverage is at least 90%.
• My code passes all unit tests and CI tests on CircleCI.