Upgrade the default setting to r6.0

[zhiqwang]

No description provided.

[codecov]

Codecov Report

Merging #213 (57c21b1) into main (ba00436) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #213   +/-   ##
=======================================
  Coverage   96.98%   96.98%           
=======================================
  Files          10       10           
  Lines         631      631           
=======================================
  Hits          612      612           
  Misses         19       19           

Flag	Coverage Δ
unittests	96.98% <100.00%> (ø)

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Impacted Files	Coverage Δ
test/test_engine.py	100.00% <100.00%> (ø)

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