put using json=nlohmann:ordered_json under namespace platform

src/best/BestResults.h

@@ -2,8 +2,9 @@
 
 #include <string>
 #include <nlohmann/json.hpp>
-using json = nlohmann::ordered_json;
 namespace platform {
+    using json = nlohmann::ordered_json;
+
     class BestResults {
     public:
         explicit BestResults(const std::string& path, const std::string& score, const std::string& model, const std::string& dataset, bool friedman, double significance = 0.05)

src/best/BestResultsExcel.h

@@ -5,10 +5,9 @@
 #include <nlohmann/json.hpp>
 #include "reports/ExcelFile.h"
 
-using json = nlohmann::ordered_json;
 
 namespace platform {
-
+    using json = nlohmann::ordered_json;
     class BestResultsExcel : public ExcelFile {
     public:
         BestResultsExcel(const std::string& score, const std::vector<std::string>& datasets);

src/best/Statistics.h

@@ -5,9 +5,9 @@
 #include <map>
 #include <nlohmann/json.hpp>
 
-using json = nlohmann::ordered_json;
-
 namespace platform {
+    using json = nlohmann::ordered_json;
+
     struct WTL {
         int win;
         int tie;