添加extra方法定义

[luxin88]

extra方法没有定义导致IDE报Warning

[codecov-io]

Codecov Report

Merging #244 (e583c10) into 2.0 (353f705) will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##                2.0     #244   +/-   ##
=========================================
  Coverage     11.85%   11.85%           
  Complexity     2840     2840           
=========================================
  Files            62       62           
  Lines          6746     6746           
=========================================
  Hits            800      800           
  Misses         5946     5946           

Flag	Coverage Δ	Complexity Δ
unittests	11.85% <ø> (ø)	0.00 <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ	Complexity Δ
src/Model.php	0.00% <ø> (ø)	137.00 <0.00> (ø)

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