Add usage examples to metric functions and improve some API docs.
Add usage examples to metric functions and improve some API docs.

PiperOrigin-RevId: 303200932
Change-Id: I18ac3d545b32975e85f3532f4c60e59e9bb05548

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