DFT PR - 8 - Githubissues

Description

Fix #(issue)

Please check the option that is related to your PR.

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
- In this case, we recommend to discuss your modification on GitHub issues before creating the PR
[x] Documentations (modification for documents)

[x] My code follows the style guidelines of this project
- [x] Run yapf -i <modified file> and check no errors (yapf version must be 0.32.0)
- [x] Run mypy -p deepchem and check no errors
- [x] Run flake8 <modified file> --count and check no errors
- [x] Run python -m doctest <modified file> and check no errors
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] I have made corresponding changes to the documentation
[x] I have added tests that prove my fix is effective or that my feature works
[x] New unit tests pass locally with my changes
[x] I have checked my code and corrected any misspellings