Early return for nest flatten when the input is None
Early return for nest flatten when the input is None

PiperOrigin-RevId: 327752828
Change-Id: I6d60c87daea1df08a8515421a85e8583c4fd2eb8

sarvex/tensorflow,frreiss/tensorflow-fred,petewarden/tensorflow,annarev/tensorflow,Intel-tensorflow/tensorflow,freedomtan/tensorflow,tensorflow/tensorflow,Intel-Corporation/tensorflow,Intel-Corporation/tensorflow,yongtang/tensorflow,davidzchen/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,yongtang/tensorflow,gautam1858/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow,aam-at/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,tensorflow/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,sarvex/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,Intel-tensorflow/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,gautam1858/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,aldian/tensorflow,annarev/tensorflow,gautam1858/tensorflow,Intel-tensorflow/tensorflow,karllessard/tensorflow,annarev/tensorflow,tensorflow/tensorflow-pywrap_saved_model,frreiss/tensorflow-fred,tensorflow/tensorflow,yongtang/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow-pywrap_saved_model,karllessard/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,gautam1858/tensorflow,Intel-tensorflow/tensorflow,Intel-Corporation/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,tensorflow/tensorflow-pywrap_tf_optimizer,aam-at/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,cxxgtxy/tensorflow,karllessard/tensorflow,Intel-tensorflow/tensorflow,davidzchen/tensorflow,tensorflow/tensorflow-pywrap_saved_model,Intel-tensorflow/tensorflow,tensorflow/tensorflow,freedomtan/tensorflow,yongtang/tensorflow,petewarden/tensorflow,Intel-Corporation/tensorflow,cxxgtxy/tensorflow,yongtang/tensorflow,yongtang/tensorflow,gautam1858/tensorflow,annarev/tensorflow,karllessard/tensorflow,karllessard/tensorflow,petewarden/tensorflow,freedomtan/tensorflow,paolodedios/tensorflow,petewarden/tensorflow,davidzchen/tensorflow,paolodedios/tensorflow,paolodedios/tensorflow,cxxgtxy/tensorflow,paolodedios/tensorflow,frreiss/tensorflow-fred,freedomtan/tensorflow,frreiss/tensorflow-fred,petewarden/tensorflow,aam-at/tensorflow,Intel-Corporation/tensorflow,annarev/tensorflow,aldian/tensorflow,davidzchen/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,karllessard/tensorflow,paolodedios/tensorflow,petewarden/tensorflow,Intel-tensorflow/tensorflow,frreiss/tensorflow-fred,annarev/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,cxxgtxy/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,tensorflow/tensorflow-experimental_link_static_libraries_once,aldian/tensorflow,annarev/tensorflow,Intel-tensorflow/tensorflow,gautam1858/tensorflow,karllessard/tensorflow,freedomtan/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,davidzchen/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow-pywrap_saved_model,annarev/tensorflow,gautam1858/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow-pywrap_saved_model,aam-at/tensorflow,karllessard/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,aam-at/tensorflow,davidzchen/tensorflow,karllessard/tensorflow,aam-at/tensorflow,aam-at/tensorflow,gautam1858/tensorflow,frreiss/tensorflow-fred,freedomtan/tensorflow,aldian/tensorflow,Intel-Corporation/tensorflow,tensorflow/tensorflow,gautam1858/tensorflow,frreiss/tensorflow-fred,cxxgtxy/tensorflow,aam-at/tensorflow,freedomtan/tensorflow,petewarden/tensorflow,sarvex/tensorflow,Intel-tensorflow/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,Intel-tensorflow/tensorflow,aldian/tensorflow,petewarden/tensorflow,tensorflow/tensorflow,petewarden/tensorflow,sarvex/tensorflow,freedomtan/tensorflow,gautam1858/tensorflow,tensorflow/tensorflow-pywrap_saved_model,tensorflow/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow-pywrap_saved_model,annarev/tensorflow,petewarden/tensorflow,paolodedios/tensorflow,annarev/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow,yongtang/tensorflow,karllessard/tensorflow,paolodedios/tensorflow,davidzchen/tensorflow,gautam1858/tensorflow,gautam1858/tensorflow,freedomtan/tensorflow,davidzchen/tensorflow,petewarden/tensorflow,cxxgtxy/tensorflow,cxxgtxy/tensorflow,sarvex/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,davidzchen/tensorflow,sarvex/tensorflow,yongtang/tensorflow,cxxgtxy/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow-pywrap_saved_model,paolodedios/tensorflow,aam-at/tensorflow,frreiss/tensorflow-fred,freedomtan/tensorflow,aldian/tensorflow,aam-at/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,Intel-Corporation/tensorflow,davidzchen/tensorflow,freedomtan/tensorflow,sarvex/tensorflow,yongtang/tensorflow,tensorflow/tensorflow-pywrap_saved_model,tensorflow/tensorflow-pywrap_saved_model,davidzchen/tensorflow,tensorflow/tensorflow-pywrap_saved_model,Intel-Corporation/tensorflow,aam-at/tensorflow,aldian/tensorflow,sarvex/tensorflow,yongtang/tensorflow,karllessard/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,freedomta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