DOC: add a graph to describe task time cost

[Zeroto521]

No description provided.

[codecov]

Codecov Report

Merging #286 (4253e30) into master (4cd078f) will decrease coverage by 1.94%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #286      +/-   ##
==========================================
- Coverage   99.70%   97.75%   -1.95%     
==========================================
  Files          28       28              
  Lines         667      667              
  Branches       75       75              
==========================================
- Hits          665      652      -13     
- Misses          0       10      +10     
- Partials        2        5       +3     

Impacted Files	Coverage Δ
dtoolkit/accessor/_util.py	80.00% <0.00%> (-20.00%)	⬇️
dtoolkit/geoaccessor/geodataframe.py	91.30% <0.00%> (-8.70%)	⬇️
dtoolkit/geoaccessor/geoseries.py	94.11% <0.00%> (-5.89%)	⬇️
dtoolkit/accessor/series.py	95.91% <0.00%> (-4.09%)	⬇️
dtoolkit/accessor/dataframe.py	93.97% <0.00%> (-3.62%)	⬇️

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