save difference to diff.csv

kpi.py

     #print('total stroke')
     #print(norm['stroke_count'].unique())
     #print(norm)
-
-    
-
+    diff_csv = norm[['frame','diff_diff']]
+    diff_csv.to_csv('./diff.csv')
     #plt.plot(norm['frame'],norm['diff_diff'])
-    #plt.savefig('/sources/diff_diff.png')
+    #plt.savefig('./diff_diff.png')