Updated to support changes to pandas styler

Author: kaklise

Diff for: examples/dashboard/dashboard_example_3.py

@@ -53,8 +53,8 @@ def color_value(val):
             metrics.style
             .format("{:.2f}")
             .applymap(color_value) 
-            .highlight_null(null_color='gray')
-            .render()
+            .highlight_null(color='gray')
+            .to_html()
         )
 
         # Store content to be displayed in the dashboard