Update app.py

app.py

@@ -76,7 +76,7 @@ def network_visualizer(yaxis, city, fstyear,lastyr, num_nodes):
 
 
     net.barnes_hut(gravity=-5000, central_gravity=0.1, spring_length=200)
-    net.show_buttons(filter_=['physics'])
+    net.show_buttons()
     html = net.generate_html()
     html = html.replace("'", "\"")