Merge branch 'update-docs' into 'master'

Format the document and add some answers of hot questions.

See merge request !858

docs/faq.md

@@ -29,6 +29,10 @@ avoiding C++ iostream, hidden internal functions etc.
 In most cases, the expected overhead should be less than
 {model weights size in float32}/2 + 3MB.
 
+How to set the input shape in your model deployment file(.yml) when your model support multiple input shape?
+------------------------------------------------------------------------------------------------------------
+Set the largest input shape of your model. The input shape is used for memory optimization.
+
 OpenCL allocator failed with CL_OUT_OF_RESOURCES
 ------------------------------------------------
 OpenCL runtime usually requires continuous virtual memory for its image buffer,

docs/user_guide/advanced_usage.rst

@@ -401,28 +401,29 @@ Reduce Library Size
 * Remove the unused ops.
 Remove the registration of the ops unused for your models in the ``mace/ops/ops_register.cc``,
 which will reduce the library size significantly. the final binary just link the registered ops' code.
-```
-#include "mace/ops/ops_register.h"
 
-namespace mace {
-namespace ops {
-// Just leave the ops used in your models
+.. code:: cpp
 
-...
+    #include "mace/ops/ops_register.h"
 
-}  // namespace ops
+    namespace mace {
+    namespace ops {
+    // Just leave the ops used in your models
 
+    ...
 
-OpRegistry::OpRegistry() : OpRegistryBase() {
-// Just leave the ops used in your models
+    }  // namespace ops
 
-  ...
 
-  ops::RegisterMyCustomOp(this);
+    OpRegistry::OpRegistry() : OpRegistryBase() {
+    // Just leave the ops used in your models
 
-  ...
+      ...
 
-}
+      ops::RegisterMyCustomOp(this);
 
-}  // namespace mace
-```
+      ...
+
+    }
+
+    }  // namespace mace