Change layers.metric to layers.metric_op

source/api_reference/gen_doc.sh

 #!/bin/bash
-python gen_doc.py layers --submodules control_flow device io nn ops tensor learning_rate_scheduler detection metric tensor > layers.rst
+python gen_doc.py layers --submodules control_flow device io nn ops tensor learning_rate_scheduler detection metric_op tensor > layers.rst
 
 for module in data_feeder clip metrics executor initializer io nets optimizer param_attr profiler regularizer transpiler recordio_writer backward average profiler
 do

source/api_reference/layers.rst

@@ -1618,8 +1618,8 @@ box_coder
 ..  autofunction:: paddle.fluid.layers.box_coder
     :noindex:
 
-metric
-======
+metric_op
+=========
 
 .. _api_fluid_layers_accuracy: