Update

app.py

@@ -2,8 +2,20 @@
 
 import gradio as gr
 
+CHOICES = ["(NONE)", "a", "b", "c"]
+
+
+def fn(choices):
+    print(choices)
+    if "(NONE)" in choices:
+        return []
+    else:
+        return choices
+
+
 with gr.Blocks() as demo:
-    pass
+    checkbox = gr.CheckboxGroup(choices=CHOICES, value=["a", "b", "c"])
+    checkbox.change(fn=fn, inputs=checkbox, outputs=checkbox)
 
 if __name__ == "__main__":
     demo.queue().launch()