Replace isinstance with private functions

[zydmayday]

No description provided.

[codecov-commenter]

Codecov Report

Merging #166 (8142cfc) into main (aef19a6) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #166   +/-   ##
=======================================
  Coverage   98.18%   98.18%           
=======================================
  Files         195      196    +1     
  Lines        1980     1988    +8     
=======================================
+ Hits         1944     1952    +8     
  Misses         36       36           

Impacted Files	Coverage Δ
ramda/map.py	100.00% <100.00%> (ø)
ramda/private/_helper.py	97.22% <100.00%> (+0.07%)	⬆️
ramda/private/_stepCat.py	100.00% <100.00%> (ø)
ramda/__init__.py	100.00% <0.00%> (ø)
ramda/lift.py	100.00% <0.00%> (ø)

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