Converge database interface and provide examples.

[AnguseZhang]

No description provided.

[codecov-io]

Codecov Report

Merging #159 into devel will increase coverage by 0.19%.
The diff coverage is 70.52%.

@@            Coverage Diff             @@
##            devel     #159      +/-   ##
==========================================
+ Coverage   23.23%   23.43%   +0.19%     
==========================================
  Files          79       79              
  Lines       13005    13058      +53     
==========================================
+ Hits         3022     3060      +38     
- Misses       9983     9998      +15

Impacted Files	Coverage Δ
dpgen/main.py	0% <0%> (ø)	⬆️
dpgen/database/run.py	72.59% <71.27%> (-3.36%)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f68ed9f...420b41d. Read the comment docs.

[codecov-io]

Codecov Report

Merging #159 into devel will increase coverage by 0.19%.
The diff coverage is 70.52%.

@@            Coverage Diff             @@
##            devel     #159      +/-   ##
==========================================
+ Coverage   23.23%   23.43%   +0.19%     
==========================================
  Files          79       79              
  Lines       13005    13058      +53     
==========================================
+ Hits         3022     3060      +38     
- Misses       9983     9998      +15

Impacted Files	Coverage Δ
dpgen/main.py	0% <0%> (ø)	⬆️
dpgen/database/run.py	72.59% <71.27%> (-3.36%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f68ed9f...420b41d. Read the comment docs.