Made 'size' parameter for OneHot Layer optional.

src/main/resources/templates/gluon/elements/OneHot.ftl

 <#assign input = element.inputs[0]>
 <#assign size = element.size>
 <#if mode == "ARCHITECTURE_DEFINITION">
-            self.${element.name} = OneHot(size=${size})
-            <#include "OutputShape.ftl">
+        self.${element.name} = OneHot(size=${size})
+        <#include "OutputShape.ftl">
 </#if>
 <#if mode == "FORWARD_FUNCTION">
         ${element.name} = self.${element.name}(${input})