fix tf-nightly broken

[haifeng-jin]

Which issue(s) does this Pull Request fix?

resolves #000

Details of the Pull Request

[codecov]

Codecov Report

Merging #1741 (81b85b1) into master (efe94d2) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1741   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           51        51           
  Lines         3411      3411           
=========================================
  Hits          3411      3411           

Impacted Files	Coverage Δ
autokeras/keras_layers.py	100.00% <100.00%> (ø)

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